Arterial aneurysms in children: Clinicopathologic classification Rajabrata Sarkar, M D , Arnold G. Coran, M D , R o b e r t E. Ciney, M D , S. Martin Lindenauer, M D , and James C. Stanley, M D , Ann Arbor, Mich. Thirty-one arterial macroaneurysms in 23 pediatric-aged patients (16 boys and 7 girls) were treated at the University of Michigan. The average age at time of diagnosis was 10.2 years (range 6 months to 18 years). Vessels involved the aorta (4), as well as hepatic (1), splenic (2), gastroepiploic (1), renal (12), iliac (1), superficial femoral (4), popliteal (1), brachial (1), radial (2), and ulnar (2) arteries. Twelve children exhibited overt clinical manifestations including presence of a mass (7), local pain (3), hematemesis (1), and painless obstructive jaundice (1). Eleven children had asymptomatic lesions. Aneurysm existence was confirmed by arteriography or operation. All but one child underwent surgical therapy, with 20 long-term survivors (mean follow-up 3.5 years). One operative death occurred and one death occurred 6 years after surgery. This experience and a review of previously reported cases served as a basis for categorization of childhood aneurysmal disease as true aneurysms associated with (I) arterial infection, (II) giant,cell aortoarteriris, (HI) autoimmune connective tissue disease, (IV) Kawasald's disease, (V) EhlersDanlos syndrome or Marfan's syndrome, (VI) other forms of noninflammatory medial degeneration, (VII) arterial dysplasias, (VIII) congenital-idiopathic factors, as well as (IX) false aneurysms associated with extravascular events causing vessel wall injury or disruption. Knowledge of the varied clinicopathologic characteristics of arterial aneurysms in children is important in treating these patients. (J VASe SugG 1991;13:47-57.)

Arterial aneurysms in childhood are rare. Only 165 pediatric-aged patients with these aneurysms, including 10 from the authors' institution, 16 have been described in the earlier literature. Previous reports usually have described solitary cases with few series from a single institution exceeding three or four cases. In part, because of the rarity of these lesions, a unified categorization of arterial aneurysms in children has not been established. This task has been hindered by the fact that firm identification of cause is often complicated by nonspecific late pathologic findings in aneurysm specimens regardless of the prior disease state responsible for their development. A clinicopathologic classification of arterial aneurysms in children that accounts for their known heterogeneity is needed. This work proposes a classification of these arterial aneurysms based on a re-

From the Sections of Vascular Surgery and Pediatric Surgery, Department of Surgery,University,of MichiganMedicalCenter, Ann Arbor. Presented at the Forty-fourthAnnualMeeting of the Societyfor Vascular Surgery,Los Angeles,Calif.,June 4-6, 1990. Reprint requests: Rajabrata Sarkar MD, c/o James C. Stanley, MD, 1500 East Medical Center Dr., 2210THC, Ann Arbor, MI 48109-0329. 24/6/25647

view of existing reports and encounters with these aneurysms at the authors' institution. UNIVERSITY OF MICHIGAN EXPERIENCE Thirty-one arterial aneurysms affecting 23 pediatric-aged patients (16 boys and 7 girls) were encountered at the University of Michigan Medical Center (UMMC) from 1957 to 1989 (Table I). Ages ranged from 2 weeks to 18 years. Aneurysms were documented by arteriography or operation. All but one child underwent surgical therapy, with 20 longterm survivors. One operative death occurred and one death occurred 6 years after operation. Followup information was obtained in all children (mean follow-up of 3.5 years). Excluded from this review were aneurysms of the intracranial arteries and coronary arteries. Brief comments on the individual arteries affected with these lesions are warranted. Aorta. Four children exhibited aortic aneurysms, three of which affected the ascending aorta and one the aortic arch. Medial degeneration was apparent in three patients, but the primary cause was undetermined in the fourth patient. Manifestations varied from no symptoms to circulatory collapse after aneurysmal rupture. Arteriography established the di47

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Table I. University of Michigan experience: childhood arterial aneurysms Patient

Age (yr) /sex

Affected artery R brachial

Size, morphologicfeatures, histologicfeatures 3 cm, fusiform, IEL fragmentation, medial thinning, mucinous deposits 1-2 cm, fusiform, absent IEL, intimal thickening, mucinous deposits 0.5 cm, saccular pseudoaneurysm, fragmentation of arterial wall with intimal and medial fibrosis Medial degeneration with intramural hemorrhage

Associated diagnoses

1

0.5 M

Kawasaki's disease

2

2M

3

2M

R superficial femoral (four discrete aneurysms) L ulnar

4

3M

Aortic arch

5

4F

R common iliac

6 cm, saccular, normal media, mild intimal fibroplasia

6

4M

Common hepatic

4 cm, saccular, absent elastic fibers, medial disruption

Kawasaki's disease

7

5M

Ascending aorta

5 cm, fusiform

Marfan's syndrome

8

5M

L radial

Arterial catheter injury

9

9M

R radial

10

9M

R renal

11

13 M

R renal L renal (three aneurysms)

12

13 F

R renal segmental

1.5 cm, saccular, chronic inflammation with organizing thrombus 1.5 cm, mural thrombus, fibrosis, no elastic lamina 1.5 cm, saccular, intimal thickening, attenuation of media 0.3 cm, saccular 1.0, 0.3, and 0.3 cm, saccular, medial thinning 1.0 cm, saccular

--

Blunt trauma

Ehlers-Danlos syndrome --

Clinical manifestations, t r e ~ t , outcome Axillary mass, excision and interposition brachial artery vein graft, excellent result: 4 years Thigh mass, excision and interposition femoral artery vein graft, excellent result: 1.5 years Wrist mass, excision with arterial anastamosis, good result Cyanosis with exertion, arch replacement with prosthetic graft, good result: 13 years Abdominal mass, excision with cross-over ilioiliac arterial graft, good resuit: 9 too. Jaundice, before surgery thought to be choledochal cyst, aneurysm ligated, good result Asymptomatic, diagnosed by ultrasonography, aortic root replacement, good result Wrist mass, excision with ligation, good result

Class IV

VI

IX

V

VIII

IV

V

IX

Arterial catheter injury

Wrist mass, excision with ligation, good result

IX

Arterial dysplasia

Asymptomatic, aortorenal bypass, good result

VII

Arterial dysplasia

Asymptomatic, R-arterial reimplantation, Lnephrectomy, good result Asymptomatic, nephrectomy, good result

VII

Arterial dysplasia

VII

R, Right; L, left; IEL, internal elastic lamina.

agnosis in all cases. Elective resection and aortic graft placement in three children was successful, whereas an operation performed on an emergency basis after cardiac arrest in the fourth child resulted in death. Hepatic artery. One child with a hepatic artery aneurysm and a past history of Kawasaki's disease sought treatment for jaundice. He was initially believed to have a choledochal cyst based on ultrasound findings. Diagnosis of a common hepatic artery aneurysm was made at operation. Excision of this lesion without arterial reconstruction proved successful. The histologic appearance of the aneurysm revealed deficient elastic tissue and medial thinning.

Splenic artery. One child with stigmata of Marfan's syndrome had two segmental splenic artery macroaneurysms identified arteriographically. These aneurysms have remained asymptomatic over 22 years' follow-up. Gastroepiploic artery. One child had massive hematemesis from a bleeding false aneurysm of the right gastroepiploic artery. This occurred after performance of a cystojejunostomy undertaken in treatment for a traumatic pancreatic pseudocyst. Subsequent aneurysm excision proved successful, Renal artery. Eight children had aneurysms of the renal artery or its branches. All were diagnosed

Volume 13 Number 1 January. 1991

Arterial aneurysms in children

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Table I. University of Michigan experience: childhood arterial aneurysms--cont'd Patient

Age (yr) ~sex

Affected artery

Size, raorphologicfeatures, histologic features

Associated diagnoses

13

13 F

Ascending aorta

12 cm, saccular, associated dissection

Thoracic coarctation

14

14 M

L renal segmental

0.4 cm, saccular

Arterial dysplasia

15

14 F

R renal

0.6 cm, saccular

Arterial dysplasia

16

14 F

R renal segmental

0.3 cm, fusiform, thickened intima with mucoid degeneration

17

15 M

Splenic segmental (two aneurysms)

Both 0.3 cm, saccular

Arterial dysplasia, neurofibromatosis Possible Marfan's syndrome

18

15 F

R renal (two aneu~sms)

1.8 cm-saccular, 0.6 cm-fusiform, medial thinning

Arterial dysplasia

19

16 M

R popliteal

6 cm, fusiform pseudoaneurysm, thrombus

Erosion by osteochondroma

20

16 M

Ascending aorta

Fusiform

Ehlers-Danlos syndrome

21

18 M

L ulnar

1.5 cm, saccular pseudoaneurysm, medial and intimal fibroplasia, increased ground substance

Blunt trauma

22

18 M

R renal

1.5 cm, saccular, intimal fibroplasia, medial thinning

Arterial dysplasia

23

18 F

R gastroepiploic

0.6 cm, saccular

Blunt abdominal trauma, pancreatitis with pseudocyst formation

during arteriography for evaluation of renovascular hypertension. No child had symptoms directly attributable to an aneurysm. Primary operations performed included aneurysmectomy and bypass (3), aneurysmectomy and vein patch angioplasty (3), aneurysmorrhaphy (1), and nephrectomy (1). All vascular reconstructions were successful except one, which resulted in a delayed nephrectomy. These aneurysms invariably exhibited medial thinning and reductions in elastic tissue. Iliac artery. One child had an asymptomatic aneurysm of the common iliac artery that appeared to be an abdominal mass and was diagnosed by arteriography. The cause of this aneurysm remains undetermined. Aneurysm excision and arterial reconstruction was successful. Femoral artery. One child with no known pre-

Clinical manifestations, treatment, outcome Chest pain, syncope, cardiac arrest, emergent operation, death Asymptomatic, aneurysm plicated, good result Asymptomatic, excision with vein patch, good result Asymptomatic, resection with vein patch, later nephrectomy Asymptomatic, incidental findings on angiogram, no treatment, no manifestations in 22 years of follow-up Asymptomatic, ligation with aortorenal vein bypass, good result Painful leg mass, excision with vein patch, good result R flank pain and R hand ischemia, aortic root replacement, died 6 years later Painful wrist mass, excision with interposition ulnar artery, vein graft, good result Asymptomatic, excision, renal revascularization with vein graft, good result Hematemesis post ~stojejunostomy, exctslon of aneurysm, good result

Class VI VII VII VII V

VII IX V

IX

VII

IX

disposing factors had four discrete aneurysms of the superficial femoral artery. These aneurysms, appearing as an asymptomatic thigh mass, were diagnosed by arteriography. They were excised, and the artery was successfully reconstructed. Microscopic examination revealed medial mucoid degeneration with fragmentation of the internal elastic lamina. Popliteal artery. One child had a tender thigh mass that was documented by arteriography to be a popliteal artery pseudoaneurysm caused by arterial erosion by an osteochondroma. Aneurysm excision and arterial reconstruction proved successful. Brachial artery. One child with a history of Kawasaki's disease had a discrete aneurysm of the proximal brachial artery demonstrated by arteriography. This was resected, and the artery was successfully reconstructed with a vein graft. The histologic ap-

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Table H . Classification o f childhood arterial aneurysms* Class

I: Arterial infection

II: Giant-cell aortoarteritis III: Autoimmune vasculitis

IV: Kawasaki's disease

Pnncipal artery(s) affected

Histologic and morphologic character

Aorta (particularly thoracic), iliac

Acute inflammatory infiltrates present initially, then chronic inflammation and fibrotic changes; saccular aneurysms Aorta, (peripheral arter- Chronic inflammation with ies, rare) giant-cells, vessel wall necrosis; saccular aneurysms Renal, hepatic and splen- Chronic panmural inflammaic arterial branches tion and degeneration, l a t e fibrosis; multiple small saccular aneurysms Corona~ (20% to 30%), Medial degeneration and fiaxillobrachial, iliobrosis; multiple small sacfemoral, hepatic cular aneurysms

V: Medial degeneration: Marfan's and EhlersDanlos syndromes

Aorta

VI: Medial degeneration: other forms

Aorta, (peripheral arteries, rare)

VII: Arterial dysplasias

Renal

VIII: Idiopathic, congenital

Uiofemoral, brachial, aorta

IX: Extravascular causes

Aorta, visceral and extremity arteries

Clinical charactemstics

Cardiovascular anomalies and umbilical artery catheterization predisposing factors; dyspnea, cough, chest pain with progression to rupture and death if untreated Signs and symptoms vary from being absent to shock; untreated aortic lesions progress to rupture Usually asymptomatic but may cause hematuria, perirenal hematomas or death with rupture Often asymptomatic; myocardial infarction or tamponade (coronary), limb ischemia (extremity), and obstructive jaundice (hepatic) may occur Aortic rupture or dissection common; arteriography and vascular reconstruction hazardous in type IV Ehlers-Danlos syndrome

Medial elastic tissue disorganization, mucinous deposits (cystic medial necrosis); solitary saccular or fusiform aneurysms Medial elastic tissue disorga- Associated with other cardiac (bicuspid nization, mucinous deposaortic valve) and aortic (coarctation) its (cystic medial necrosis); anomalies; often present with aortic solitary saccular aneurysms dissection or rupture Medial thinning and fibropla- Usually asymptomatic, detected during arreriography for renovascular hysia; solitary and multiple saccular aneurysms affectpertension ing arterial bifurcations most often Secondary. intimal fibroplasia; Often asymptomatic, but may cause limb ischemia; rupture unreported saccular, usually solitary, symmetrical if multiple Disruption of usual three lay- Protean manifestations; aortic aneuers of artery, fibrosis and rvsms often rupture; peripheral lemural thrombus; saccular sions often asymptomatic; visceral aneurvsms lesions may cause gastrointestinal bleeding

*Based on a review of 135 reported cases and those in the current report. Excludes aneurysms of the intracranial and coronary arteries.

pearance o f this aneurysm was o f medial thinning and fragmentation o f the internal elastic lamina. R a d i a l artery. T w o children had aneurysms o f their radial artery after catheter insertion. B o t h were d o c u m e n t e d by arteriography and were treated successfully by excision and arterial ligation. U l n a r artery. Aneurysms o f the ulnar artery developed in t w o children after h a n d trauma. B o t h were diagnosed by arteriography. T h e y were treated successfuUy by excision with primary reanastomosis in one child and vein graft reconstruction in the other.

D E S C R I P T I O N OF C L I N I C O P A T H O L O G I C CLASSES Classification o f arterial aneurysms affecting children into specific categories should provide a better understanding o f their clinical relevance. T o this end,

g r o u p i n g o f these arterial aneurysms into nine classes is p r o p o s e d (Table II). Class I : a n e u r y s m s c a u s e d b y arterial i n f e c t i o n ( n o U M M C cases). These aneurysms are a m o n g the m o r e c o m m o n arterial aneurysms in childhood, acc o u n t i n g for a third o f the reported cases. T h e y usually exhibit evidence o f infection o n microscopic examination o r culture. These aneurysms, often referred to as mycotic aneurysms, usually result f r o m destruction o f the arterial wall by h e m a t o g e n o u s seeding o f microbes into the artery as a consequence o f a systemic infection, such as endocarditis o r bacteremias. I n contradistinction, secondary arterial infection arising f r o m direct invasion by a paravascular infection, such as an adjacent abscess, causes false aneurysm formation, and is m o r e appropriately placed in class IX. A differential diagnosis o f these

Volume 13 Number 1 ]anuaq, 1991

two aneurysm types is often based on clinical information, not the histologic character of the aneurysm. A total of 5 1 children in class I have been previously described in the literature. 7`z° Of the reported cases, the aorta was affected in 47 patients, and iliac artery was involved in four patients. These aneurysms occurred in pediatric patients of all ages. Before the development of antibiotics, bacterial endocarditis was the most common cause38 Staphylococcus and Streptococcus bacteria have been the most common infective organisms reported, although viral and fungal agents also have been encountered. 13'2°Histologic examination may reveal an early acute inflammatory infiltrate, or later chronic inflammation with or without fibrosis. Most currently encountered aneurysms are associated with a wide range of predisposing conditions, such as umbilical artery catheterization, an aortic coarctation, or a bicuspid aortic valve. Infectious aneurysms associated with aortic coarctation usually involve the aorta immediately distal to the site of narrowing. H'~4The average age of 17 years in patients having infectious aneurysms and aortic coarctation is much lower than the average age of 37 years in patients with noninfectious aneurysms associated with aortic coarctation." Clinical presentation of infectious aneurysms almost always includes a present or prior febrile illness. Thoracic aortic aneurysms in infants may cause choking with feeding, cough, dyspnea, or frank respiratory compromise. Older children may have voice changes, dysphagia, chest pain, and respiratory symptoms. Occasional patients have a triad of fever, hematuria, and diminished femoral pulses. These findings are highly suggestive of a bacterial endarteritis with aortic coarctation. Infectious thoracic aneurysms progress to rupture if untreated/7 Death in younger children with thoracic aortic aneurysms is usually due to compression of adjacent structures, causing airway obstruction or compromised aortic outflow/6 Infectious abdominal aortic aneurysms in children may be asymptomatic, and are not always evident on physical examination? Infectious lilac aneurysms are usually asymptomatic. 19 Early resection and aortic reconstruction of infected thoracic aneurysms is necessary for survival, whereas abdominal aortic lesions may be treated more conservatively.16 Infectious iliofemoral aneurysms should usually be repaired with restoration of distal extremity flow to avoid subsequent limb-length growth disturbances. Class II: aneurysms with giant-cell aortoarteritis (no UMMC cases). Aneurysms in this category are rare. These ancurysms exhibit microscopic evidence of giant-ccll infiltratcs with destruction of

Arterial aneurysms in children

51

the normal vessel wall architecture. Six children with these lesions have been reported. 21.26They most commonly affect the aorta, although peripheral aneurysms of this type have been described. 22,24 Clinical presentations vary from asymptomatic aneurysms discovered during routine examination to hemorrhage after rupture. 22'24'2s The natural history of untreated giant-cell aneurysms is chracterized by progression to rupture and death. Although these chronic inflammatory aneurysms have been described in children with Takayasu's arteritis, 23 the presence of giant cells in an aneurysm may occur in patients without other characteristics of this disease. 26 Resection and aortic reconstruction is appropriate in treating these aneurysms. Class III: aneurysms with autoimmune connective tissue disease (no UMMC eases). These aneurysms usually exhibit acute inflammatory changes, although neutrophils may not be present in long-standing aneurysms. Most children with these lesions have had clinical features of an autoimmune vasculitis, such as polyarteritis nodosa (PAN). Five children with these aneurysms have been reported. 27-s°These children often have fever, mucous membrane inflammation, and diminished renal function. Although aneurysms associated with PAN may occur throughout the entire vascular system, the most commonly affected vessels are those of the kidney (80% to 100%), liver (50% to 60%), and spleen (45%).28 Multiple aneurysms of the arteries in these organs may be evident as early as 1 week after the onset of systemic symptoms. 2g Fibrinoid necrosis followed by a chronic inflammatory endarteritis is characteristic of PAN. Aneurysms developing as a consequence of PAN exhibit chronic inflammatory and degenerative changes. Microaneurysms are most common, although macroaneurysms exceeding 3 mm usually are evident in this class. Aneurysms related to PAN in children are usually asymptomatic. 29 Those aneurysms most likely to become symptomatic affect the renal vessels, with their thrombosis or rupture causing hematuria or painful retroperitoneal-perirenal hematomas, z8 Rupture of PAN-related splanchnic artery aneurysms into the peritoneal cavity also has been recognized and may cause acute abdominal pain and s h o c k s Ligation of ruptured or symptomatic aneurysms affecting small arteries' represents conventional therapy. 27 However, rcvascularization may be necessary when treating the rare lesion involving a major visceral vessel. Infants are more frequently affected by PAN-related coronary artery aneurysms. In this regard, infantile PAN and Kawasaki's disease are often indistinguishable. "~ Class IV: aneurysms with Kawasaki's disease

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(2 U M M C cases). These aneurysms usually exhibit chronic inflammation, medial degeneration, and fibrosis. Chronic lesions may not reveal inflammation. The most important feature of these aneurysms is their coexistance with a history of Kawasaki disease (mucocutaneous lymph node syndrome). The latter is an acute febrile illness characterized by a panarteritis, sterile conjunctivitis, a desquamating rash, erythema and fissuring of the lips, as well as edema of the hands and feet. Fifteen children with these aneurysms, including two in this series have been reported. ~'32-36Aneurysms of the coronary arteries occur in 20% to 30% of children having Kawasaki's disease, with other arteries, especially the axillobrachial and iliofemoral vessels, being involved less often. Clinical manifestations of aneurysms related to Kawasaki's disease are most serious when associated with thrombosis and myocardial infarction or rupture and pericardial tamponade in the case of coronary artery lesions. 34 AxiUobrachial and iliofemoral aneurysms commonly occur as painless masses, but fatal rupture and ischemic gangrene have been seen. 34 Hepatic artery aneurysms may occur with obstructive jaundice and have been misdiagnosed as choledochal cysts.~,3s Gastrointestinal or biliary tract hemorrhage occurs if they rupture. Kawasaki's disease with atypical symptoms is often difficult to diagnose. Because of this, any child with a peripheral arterial aneurysm of unknown origin should be evaluated for aneurysms of the coronary vessels. Similarly, children with known Kawasaki's disease should undergo long-term serial assessments of both their coronary and peripheral arteries. Revascularization is important in the treatment of aneurysms affecting both the coronary and peripheral circulations in these children. Class V: aneurysms with medial degeneration in Marfan's syndrome and Ehlers-Danlos syndrome (4 UMMC cases). Aneurysms in this group are very uncommon. Four children with Marfan's syndrome have been reported to have arterial aneurysms, including two in this series. 33"33Similarly, five children with Ehlers-Danlos syndrome have been reported to have these aneurysms, including two in this series. 39-43 Marfan's syndrome is an autosomal dominant genetic disease of connective tissue including disorders of vessel elastin leading to cystic medial degeneration. Abnormal elastic tissue in these cases predisposes to aortic dissections and rupture as well as aneurysm formation. These lesions are recognized most commonly in the ascending aorta during the third and fourth decades of life. Clinical manifestations of aortic aneurysms in children with Marfan's syndrome

vary from mild dyspnea to cardiovascular collapse. 37,33 Aortic replacement is often necessary in managing these aneurysms. The eventual fate of untreated children with these unusual aortic aneurysms is death. Ehlers-Danlos syndrome (EDS) represents a group of diseases with a variety of underlying biochemical defects affecting connective tissue. They are genetic in origin, with both autosomal dominant and recessive forms, depending on the specific subtype. The most serious forms of EDS are usually inherited in a dominant fashion. Children with type I and IV EDS may have spontaneous bowel perforation as well as arterial rupture of aneurysm formation. Type IV EDS is caused by abnormal or absent type III collagen in vessels, skin and bowel, and is most likely to exhibit serious arterial complications. EhlersDanlos syndrome predisposes to decreased and disorganized elastic fibers, mucinous deposits in the media, and degeneration of the musuclar component of the media resembling cystic medial necrosis. 39'41 Although multiple aortic and peripheral arterial aneurysms have been reported in adults with EDS, 4°'41 aneurysms in children with EDS usually involve the a o r t a . 39,42

Clinical manifestations of aneurysms related to EDS, with few exceptions, are similar to those occurring in Marfan's syndrome. Unfortunately, accurate definition of aneurysms in EDS is hampered by severe complications associated with arteriography, occurring in 67% of these cases, particularly in EDS type IV? 4 Severe hemorrhage, vessel dissection, rupture, thrombosis, as well as death may follow arteriography or arterial puncture in these individuals. The prognosis for patients with arterial complications of type IV EDS is poor, with 63% of patients with EDS type IV dying of their disease. 44Treatment of EDS is limited by the friable nature of the vessels and soft tissues and the high rate of vessel rupture and bleeding after surgery. External compression and vessel control with large surgical tapes have been advocated in place of conventional vascular reconstructive procedures in these patients. Class VI: aneurysms associated with other forms o f noninflammatory medial degeneration (2 U M M C cases). There are two subgroups in class VI, both being associated primarily with aneurysms of the aorta. In the first subgroup most aneurysms occur as isolated lesions in otherwise healthy children. On rare occasions certain obvious inherited diseases such as tuberous sclerosis and cystinosis may be associated with these aneurysms. 43,~ Seventeen children with

Volume 13 Number 1 Janua~ 1991

isolated aneurysms in this class, including one child in this series, have been described in the literature? ss9 Degeneration or disruption of the muscular and elastic components cause cystic changes in the media of these aneurysms, yet the cause remains largely unknown. An underlying genetic defect is supported by familial occurrences of these aneurysms, s° In tuberous sclerosis an obliterative hyperplasia of the vasa vasorum is believed to cause medial ischemia and subsequent aneurysmal degeneration, ss Aneurysms in this first subgroup most often affect the descending thoracic (2 5 %) and abdominal (3 8 %) aortas, s7 The subclavian artery (19%) and the ascending aorta (6%) are less frequent sites of solitary lesions. 4s,sl's4,s8 Multiple aneurysms also have been noted in these patients (13%). ss's9 Aneurysms in this subgroup often occur with aortic dissection and neurologic deficits caused by spinal cord ischemia? 9 Shock may occur as a resuk of rupture and bleeding as well as acute aortic valve insufficiency or cardiac tamponade. Symptomatic lesions, particularly those involving aortic dissection, invariably have a poor outcome. Peripheral aneurysms in this subgroup usually occur as painless masses, but their natural history is uncertain. The second subgroup in class VI involves aortic aneurysms in children having coexisting cardiac or underlying aortic abnormalities. The most common associated lesions are bicuspid aortic valves and aortic coarctations, often with cystic medial necrosis. 6°-62A total of 17 children with aneurysms in the second subgroup have been described, including one child in this series. 61-68Aneurysms in children with bicuspid aortic valves without coarctation almost invariably are located in the ascending aorta, whereas in children with coarctation, aneurysms occur in the ascending (50%), arch (8%), as well as the descending (42%) aorta. 6s'66 Disruptive hemodynamic effects caused by the associated cardiac or aortic anomalies are thought to be important contributors to this second subgroup of aneurysms. 64'67 However, aortic aneurysms have been reported as distant as the aortic bifurcation in children with thoracic coarctations, 6s as multiple saccular aortic aneurysms, 68 and as a diffuse aortic aneurysm occurring 10 years after coarctation repair. ~2 It is important to note that both aneurysm walls and nonaneurysmal arteries in children with coarctation or bicuspid aortic values exhibit cystic medial necrosis throughout the arterial system including the pulmonary vasculature. 6°62 This suggests the presence of a systemic disease process in this class. Children with Turner's syndrome have a 15% to 36% inci-

Arterial aneurysms in children 53

dence of aortic coarctation and may on rare occasions exhibit aneurysms in this class.62 Clinical presentation of aneurysms in the second subgroup frequently involves signs and symptoms of dissection. Sudden death after vague complaints of chest pain affected 50% of these children. Operations performed on an emergency basis for class VI aortic aneurysms after circulatory collapse were uniformly unsuccessful. Earlier operation was life saving in nearly 40% of these children. Class VII: aneurysms associated with vascular dysplasias (8 U M M C cases). Aneurysms in this class affect muscular arteries and occur frequently at bifurcations. The involved vessels are usually affected with recognizable dysplastic disease. These aneurysms do not occur in the aorta. There have been 27 children with aneurysms in this class, including eight in the present series. ~'s'6972 Aneurysms associated with dysplasia may develop as a consequence of hypertension in an artery with a paucity of elastic tissue at bifurcations. The most commonly affected vessel is the renal artery. The histologic appearance of these lesions is of a thin fibrous aneurysmal wall, with a reduction in recognizable medial smooth muscle and no inflammatory cells? These aneurysms are almost always asymptomatic, although an occasional patient may have distal embolization of aneurysmal thrombus. Treatment of renal artery aneurysms usually involves aneurysmectomy or aneurysmorrhaphy at the time of renal revascularization for renovascular hypertension? Experience with extrarenal aneurysms in this class is anecdotal. Class VIII: congenital-idiopathic aneurysms unassociated with vessel wall degeneration or distant cardiovascu!ar disease (1 U M M C case). These are rare aneurysms with only Six known cases including one child in this series, r3-TzBoth solitary and multiple aneurysms occur in this class. Their cause remains unknown. The only common histologic abnormality seen in these thin-walled fibrous lesions is intimal fibroplasia, which probably reflects a secondary process rather than an etiologic factor. The involved vessels in these children, unlike those in class VII cases, do not exhibit dysplastic changes. Idiopathic aneurysms tend to arise in the abdominal aorta as well as in the axillobrachial and iliofemoral vessels. The renal arteries may be involved in children having multiple aneurysms. 76,77 With the exception of one report of an asymptomatic splenic artery aneurysm, 73 the splanchnic vasculature appears spared in this class. Clinical presentations vary according to the vessel affected. Aortic aneurysms are usually symptomatic.

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Extremity aneurysms most commonly occur as pulsatile masses, occasionally with embolic complications. These larger aneurysms should be resected and the involved vessel reconstructed. Small asymptomatic aneurysms in this class appear relatively stable without subsequent r u p t u r e . 73,w Class IX: false aneurysms caused by extravascular processes causing vessel wall injury or disruption (6 U M M C cases). These aneurysms are caused by a wide variety of paravascular infectious, inflammatory, and traumatic processes that disrupt or destroy the arterial wall. Only 11 children have been reported with this class of aneurysm, six of whom are included in this r e p o r t . 6"rs's° Because these lesions are usually not noteworthy, it is likely that there are many more patients in this class who have not been described in the literature. Erosions from adjacent tuberculous lymph nodes or infected macroemboli (not a simple bacteremia with infection of the vessel, as occur in class I aneurysms), rs-79 adjacent abscesses, s° pancreatitis, 6 and both external and intraarterial trauma are known to cause aneurysms in this class. Tuberculous involvement of hilar lymph nodes may lead to inflammation and infection of the adjacent thoracic aorta with subsequent aneurysm formation and rupture. Mononuclear infiltrates and necrosis of the adventitia and media occur in these aneurysms. Pseudoaneurysms arising from destruction of the abdominal aortic wall by other forms of abscesses may be clinically covert, and the vascular lesion may not be detected until operation for the infectious process. 8° Aneurysms of visceral vessels caused by pancreatitis, although uncommon in children, may occur with gastrointestinal hemorrhage. Localization by angiography and surgical therapy are necessary for survival. Penetrating trauma and injury from arterial cannulation can result in aneurysm formation both distal to and at the site of arterial entry. Treatment of class IX aneurysms is by means of conventional arterial reconstructive surgery and is dependent on the location and origin of the aneurysm. Arterial aneurysms in children represent a heterogeneic group of diseases. Among the 178 known aneurysms in children, including the 165 previously reported cases and the 13 new cases in the present series, only 164 had data sufficient to allow their classification. Recognition of differences in these childhood aneurysms, as proposed in the clinicopathologic classes described in this report, is important when considering appropriate diagnostic and therapeutic interventions for these unusual lesions.

REFERENCES

1. Marks WH, Coran AG, Wesley JR, ct al. Hepatic artery aneurysm associated with the mucocutaneous lymph node syndrome. Surgery 1985;98:598-9. 2. Sarkar R, Cilley RE, Coran AG. Abdominal aneurysms in childhood. Surgery (In press).

3. Stanley JC, Fry WJ. Pathogenesis and clinical significance of splenic artery aneurysms. Surgery 1974;76:898-909. 4. Stanley JC, Fry Wl. Pediatric renal artery occlusive disease and renovascular hypertension. Etiology,, diagnosis and operative treatment. Arch Surg 1981;116:669-76. 5. Stanley JC, Rhodes EL, Gewertz BL, Chang CY, Walter JF, Fry WJ. Renal artery macroaneurysms: significance of macroaneurysmsexclusive of dissections and fibrodysplastic mural dilations. Arch Surg 1975;110:1327-33. 6. StanleyJC, Thompson NW, Fry, WJ. Splanchnic artery aneurysms. Arch Surg 1970;101:689-97. 7. Bergsland J, Kawaguchi A, Roland JM, Pieroni DR~ Subramanian S. Mycotic aortic aneurysms in children. Ann Thor Surg 1984;37:314-8. 8. Cooley DA, Taylor FM. Aneurysm of thoracic aorta in an infant. J Pediatr 1956;49:185-90. 9. Drucker DE, Greenfield LJ, Ehrlich F, Salzberg AM. Aortoiliac aneurysms following umbilical artery catheterization. J Pediat Surg 1986;21:725-30. 10. Edwards JE. Aneurysms of the thoracic aorta complicating coarctation. Circulation 1973;58:195-201. 11. France NE, Levin B, McNicholl B. Coarctation of the aorta (adult wpc) with rupture distal to the coarctation, Arch Dis Child 1950;25:175-85. 12. Fricker FJ, Park SC, Neches WH, Mathews RA, Lcrberg DB. Aneurysm of the aorta in children. Chest 1979;76:305-9. 13. Khoss AE, Ponhold W, Pollak A, Schemmer M, Weninger M. Abdominal aortic aneurysm in a premature neonate with disseminated candidiasis. Pediatr Radiol 1985;15:420-1. 14. Oldham HN, Phillips JF, Jewett PH, Chen JT. Surgicaltreatment of mycotic aneurysm associated with coarctation of the aorta. Ann Thorac Surg 1973;15:411-8. 15. Park IS, Pinsky WW, Baker CJ. Ruptured mycotic aneurysm of abdominal aorta: successful treatment in a child. Am J Dis Child 1981;135:570-1. 16. Roques X, Choussat A, Bourdeaud'hui A, Laborde N, Baudet E. Aneurysms o f the abdominal aorta in the neonate and infant. Ann Vase Surg 1989;3:335-40. 17. Schneider JA, Rheuban KS, Crosby IK. Rupture of postcoarctation mycotic aneurysms of the aorta. Ann Thorac Surg 1979;27:185-90. 18. Stengel A, Woelferth CC. Mycotic (bacterial) aneurysms of intravascular origin. Arch Int Med 1923;31:527-54. 19. Todd DW, Leigh JE, Miller RH, Votava HJ. True aneurysm formation in a 6-month-old child. J Ped Surg 1984;19: 310-1. 20. Wood BP, Young LW, Elbadawi NA. Primary mycotic aneurysm in infancy and childhood. AJR 1973;118:109-15. 21. Gelfand M. Giant cell arteritis with aneurysmal formation in an infant. Br Heart J 1955;17:264-6. 22. HoUemanJH, Martin BF, Parker JH. Giant cell arteritis causing brachial artery aneurysm in an eight-year-oldchild. J Miss Med Assoc 1983;12:327-8. 23. Kozuka T, Nosaki T, Sato K, Tachiiri H. Aneurysm associated with aortitis syndrome. Acta Radiol [Diagn] (Stockholm) 1968;7:314-20.

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24. Wagenvoort CA, Harris LE, Brown AL, Veeneklaas GM. Giant-cell arteritis with aneurysm formation in children. Pediatrics 1963;32:861-7. 25. Zumbro GL, Hemley LB, Treasure RL. Saccular aneurysm of ascending aorta caused by granulomatous aortitis in a child. J Thorac Cardiovasc Surg 1975;69:397-401. 26. Wiggehnkhuizen J, Cremin BJ. Takayasu's arteritis and renovascular hypertension in childhood. Pediatrics 1978;62: 209-17. 27. Almgren B, Eriksson I, Foucard T, Lorehus LE, Olsen L. Multiple aneurysms of visceral arteries in a child with polyarteritis nodosa. J Pediatr Surg 1980;15:347-8. 28. Bron KM, Strott CA, Shapiro AP. The diagnostic value of angiographic observations in polyarteritis nodosa. Arch Int Med 1965;116:450-4. 29. Herschman A, Blum R, Lee YC. Angiographic findings in polyarteritis nodosa. Radiology 1970;94:147-8. 30. Roberts FB, Fetterman GH. Polyarteritis nodosa in infancy. J Ped 1963;63:519-29. 31. Fetterman GH, Hashida Y. Mucocutaneous lymph node syndrome (MLNS): a disease widespread in Japan which demands our attention. Pediatrics 1974;54:268-70. 32. Canter CE, Bower RJ, Strauss AW. Atypical Kawasaki disease with aortic aneurysm. Ped 1981;68:885-8. 33. Chamberlain JL, Perry LW. Infantile periarteritis nodosa with coronary and brachial aneurysms. J Ped 1971;78:1039-42. 34. Fukushige J, Nihill MR, McNamara DG. Spectrum of cardiovascular lesions in mucocutaneous lymph node syndrome. Am J Cardiol 1980;45:98-109. 35. Lipson MH, Ament ME, Fonkalsrud EW. Ruptured hepatic artery aneurysm and coronary artery aneurysms with myocardial infarction in a 14-year-old boy. J Pediatr 1981;98: 933-6. 36. Sasaguri Y, Kato H. Regression of aneurysms in Kawasaki disease. J Ped 1982;100:225-31. 37. Durnin RE, Lindesmith G, Meyer B, Flyer DC. Aorta surgery in a child with Marfan's syndrome. Amer J Dis Child 1965;110:547-50. 38. Takayanagi K, AI-Bader M. Ruptured abdominal aortic aneurysm in a 7-year-old girl. J Pediatr Surg 1983;18: 193-195. 39. Burnett HF, Bledsoe JH, Char F, Williams GD. Abdominal aortic aneurysmectomy in a 17-year-old-patient with EhlersDanlos syndrome. Surgery 1973;74:617-20. 40. Haynes CD, Smith RB, Dempsey RL, Darden WA. Multiple congenital aneurysms associated with spontaneous vascular rupture. Surgery 1982;92:910-2. 41. Imahori S, Bannerman RM, Graf CJ, Brennan JC. EhlersDanlos syndrome with multiple arterial lesions. Am J Med 1969;47:967-77. 42. Lynch HT, Larsen AL, Wilson R, Magnuson CL. EhlersDanlos syndrome and congenital arteriovenous fistulae. JAMA 1965;194:163-6. 43. Serry C, Agomuoh OS, Goldin MD. Review of EhlersDanlos syndrome. J Cardiovasc Surg 1988;29:530-4. 44. Cikrit CF, Miles JH, Silver D. Spontaneous arterial perforation: The Ehlers-Danlos specter. J VASCSURG1987;5:24854. 45. Hagood CO, Garvin DD, Lachina FL, Polsky WS, Ball TP, Bobroff LM. Abdominal aortic aneurysm and renal hemartoma in an infant with tuberous sclerosis. Surgery 1976; 79:713-5.

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46. Strayer DS. Cystinosis and a dissecting aortic aneurysm in a 7-year-old boy. Am J Dis Child 1979;133:436-7. 47. Ball RY. Ruptured abdominal aortic aneurysm in a stillborn fetus. Virchows Arch 1983[A]399:237-44. 48, Dormandy JA, Barkley H. Bilateral axillary aneurysms in a child. Br J Surg 1979;66:650. 49. Fikar CR, Amrhein JA, Harris JP, Lewis ER. Dissecting aortic aneurysm in childhood and adolescence. Clin Pediatr 1981;20:578-83. 50. Griffiths GJ, Hayhurst AP, Whitehead R. Dissecting aneurysm of the aorta in mother and child. Br Heart J 1951; 13:364-8. 51. Hartwell AS, Ewing GM. Aneurysm of the thoracic aorta in infancy. Postgrad Med 1954;16:546-52. 52. Hassler O. Media defects in human arteries. Angiology 1963;14:368-71. 53. O'Hara PJ, Ratliff NB, Graor RA, Novick A, Beven EG. Medial agenesis associated with multiple extracranial peripheral and visceral arterial aneurysms. J VAse SURG1985;2:298306. 54. Persaud V. Subclavian artery aneurysm and idiopathic cystic medionecrosis. Br Heart J 1968;30:436-9. 55. RoVes DB, Towbin R, Bove KE. Vascular dysplasia in a child with tuberous sclerosis. Pediatr Path 1985;3:359-72. 56. Sterpetti AV, Hunter WJ, Schultz RD. Congenital abdominal aortic aneurysms in the young. J VAse SURG 1988;7:763-9. 57. Strauss RG, McAdams AJ. Dissecting aneurysm in childhood. J Pediatr 1970;76:578-84. 58. Taheri SA" Turecki D, Lazar L, Warnock R. Congenital subclavian aneurysm in a four year old male. Angiology 1974; 25:769-72. 59. Williams JL. Multiple aneurysms in a child. Proc R Soc Med 1975;68:523-5. 60. Coleman PN. A case of dissecting aneun,sm in a child. J Clin Path 1955;8:313-7. 61. McKusick VA. Association of congenital bicuspid aortic valve and Erdheim's cystic medial necrosis, (Letter) Lancet 1972; 1: 1026-7. 62. Strader WJ, Wachtel HL, Lundberg GD. Hypertension and aortic rupture in gonadal dysgenesis. J Pediatr 1971;79: 473-5. 63. Becker RM, Poirier NL, Collins GF, Rosales JK, Mulder DS. Cystic medial necrosis and dissecting aneurysm of the aorta in a child with congenital aortic stenosis. J Thorac Cardiovasc Surg 1974;68:108-11. 64. Chen S, Baruer HB, Fagan LF, Kaiser GC, Mudd JF, Willman VL. Aortic aneurysm in childhood. J Pediatr 1976;89: 231-4. 65. Darden WA" Fulenwider JT, Smith RB, Sewell CW. Congenital abdominal aortic aneurysms. Surgery 1984;96:56773. 66. Huntington RW, Hirst AE. Dissecting aneurysm of the aorta in a 16-year-old girl. Am J Clin Path 1967;48:44-8. 67. McKusickVA, Logue RB, Bahnson HT. Association of aortic valvular disease and cystic medial necrosis of the ascending aorta. Circ 1957;16:188-94. 68. Pierce WS, Vencest WR, Fitzgerald E, Miller FJ. Coarctation of the abdominal aorta with multiple aneurysms. Ann Thor Surg 1975;20:687-93. 69. Flynn MP, Buchanan JB, Neurofibromatosis, hypertension, and renal artery aneurysms. South Med J 1980;73:618-20. 70, Kawamura J, Hosokawa S, Yoshida O, Angioplastic surgery

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for renal artery aneurysm in pediatric hypertension. Urol Int 1976;31:368-73. Lorentz WB, Browning MC, D'Souza VJ, Glass TA, Formanek AG. Intrarenal aneurysm of the renal artery in children. Am J Dis Child 1984;138:751-4. Nomura Y, Mizoguchi H, Sakamoto S, Ogata J. Giant renal artery aneurysm in a child. Eur Urol 1982;8:331-3. Fee H, McGough E. Idiopathic multiple systemic aneurysms in a child. Am J Dis Child 1983;137:1101-2. Howorth MB. Aneurysm of abdominal aorta in the newborn infant. N Engl J Med 1967;276:1133-4. Jones TR, Frusha JD, Stromeyer FW. Brachial artery aneurysm in an infant. J VASCSURG 1988;7:439-42.

DISCUSSION Dr. R o n a l d Busuttil (Los Angeles, Calif.). This comprehensive report on a rare, but devastating vascular lesion, has brought to our attention a spectrum o f disease that is almost solely identified with an adult population. However, as was illustrated in the presentation, aneurysms in children are caused by a variety o f pathologic disorders, which extend beyond currently held concepts that pediatric aneurysms are due only to congenital alterations o f connective tissue deposition. In contradistinction, a significant number o f aneurysms found in children have a cause similar to that seen in adults. Furthermore, the important message is that like adult aneurysms, pediatric aneurysms are surgical lesions and demand prompt intervention. There is little role for nonoperative management o f these lesions, since the natural history is a relentless progression to rupture, thrombosis, limb loss, or death. A crucial issue in the treatment o f pediatric aneurysms is that revascularization must be made a priority; whereas, certain aneurysms involving the extremities o f adults may be treated with ligation and excision, in children it is essential to perform revascularization to prevent retardation o f extremity growth. This surgical maxim is important to bear in mind when confronted with a child with an abdominal aortic aneurysm. As in adults, these aneurysms will eventually rupture when expansion is greater than 1.5 to 2 times the diameter o f the proximal aorta, which in the child may be less than 5 to 6 ram. In most cases the cause will be related to Kawasaki's disease, infection, trauma, fibromuscular dysplasia, or a connective tissue disorder such as Ehlers-Danlos syndrome. In all o f these conditions, except for Ehlers-Danlos, the treatment is aortic aneurysm resection with reconstruction with use o f a small diameter Dacron graft. Plication o f the proximal or distal anastomosis may be required. In contradistinction, children with aortic aneurysms caused by Ehlers-Danlos syndrome present a particularly difficult problem. Pathologically, as was mentioned, there

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76. Schiller M, Gordon R, Shifrin E, Khalil A. Multiple arterial aneurysms. J Pediatr Surg 1983;18:27-9. 77. Short DW. Multiple congenital aneurysms in childhood. Br J Surg 1978;65:509-12. 78. Calvin JK, Nichamin SJ. Thoracic aortic aneurysms in children. Am 1"Dis Child 1934;48:780-90. 79. Kinare SJ. Aortitis in early life and its association with tuberculosis. J Pathol 1970;100:69-76. 80. Klein RL. Abdominal aortic aneurysm in infancy subsequent to perinephric abscess. J Pediatr Surg 1986;21:451-3.

is abnormal or absent type III collagen, which provides most vessel wall tensile strength. Thus conventional reconstruction with graft replacement is contraindicated since the native aorta is friable and fractures with suture placement. Although ligation, external compression, and vessel control with broad surgical tapes has been advocated for this condition, none o f these techniques has achieved a consensus o f approval on their utility. At UCLA, since 1983, we have had experience with seven cases of pediatric aneurysms. O f these, three had Kawasaki's disease, one had a mycotic hepatic aneurysm, one had Ehlers-Danlos with aortic and popliteal artery involvement, and two had splenic artery aneurysms caused by alpha-1 antitrypsin deficiency associated with portal hypertension. Our pediatric cardiology group has had a particular interest in Kawasaki's disease, which is an acute febrile syndrome o f unknown origin seen predominantly in children less than 9 years o f age. The most serious sequelae are cardiovascular and include aneurysms o f the coronary arteries and other central and peripheral vessels. Thrombosis, rupture, and myocardial infarction are the rule. The association with lethal coronary disease is so close that all patients with the suspected syndrome should have echocardiography or coronary arteriography. At UCLA, because o f our volume o f liver transplant patients, we are recognizing more adults and children with splenic artery aneurysms. In the past 3 years we have treated five patients with these lesions, two o f which were children. One 13-year-old child died 6 days after liver replacement with a ruptured splenic artery aneurysm. The second underwent an uneventful transplant after treatment of the aneurysm was accomplished before surgery with selective embolization. We believe it is essential to screen all patients with portal hypertension for splenic artery aneurysms, since their incidence is between 25% to 30%. Furthermore, these aneurysms may occur more commonly in children with alpha-1 antitrypsin deficiency because o f the increased collagenolysis that occurs in this group o f patients.

Volume 13 Number 1 January 1991

Based on your classification, how have you altered your approach to the treatment of these pediatric patients? Second, how would you treat a 7-year-old child with EhlersDanlos who has a 3 cm infrarenal abdominal aortic aneurysm? Third, have you had any experience with the use of gamma globulin in patients who have had Kawasaki's disease in regard to regression of aneurysmal growth? And finally, for the sake of completion, where would you place splenic artery aneurysms caused by portal hypertension in your classification? Dr. Sarkar. The practical considerations of classifying pediatric arterial aneurysms become relevant when approaching, for example, an isolated peripheral aneurysm. A tentative diagnosis of Kawasaki's disease versus polyarteritis nodosa in such a case would mandate an evaluation of the coronary arteries for aneurysms. Similarly, a diagnosis of Ehlers-Danlos syndrome in a similar child would affect not only treatment of the lesion, but also initiate a screening of relatives, because of the genetic nature of this disease. With respect to the young child with Ehlers-Danlos syndrome and an aortic aneurysm, it is most important to determine which of the nine types of Ehlers-Danlos syndrome is present. Only 4% have type IV, which is associated with serious complications of surgery as well as arteriography. Unfortunately, type IV Ehlers-Danlos patients do not have classic stigmata of the disease. Diagnosis is determined best by identifying decreased production of type III collagen in skin fibroblast cultures. The use of DNA probes may provide a more accurate diagnoses in the future. We would recommend repair of an aortic aneurysm in all instances, except in a child with type IV Ehlers-Danlos syndrome, where operation would be contraindicated because of the excessive mortality rate associated with surgical therapy. However, should a lesion such as this become life-threatening, ligation alone, if posible, may be the treament of choice. Although we have not used gamma globulin for the

Arterial aneurysms m children $7

treatment of Kawasaki's disease-associated aneurysms, the concept of aneurysmal regression deserves comment. Regression is observed in most aneurysms accompanying Kawasaki's disease, occurring by two mechanisms. One is myointimal thickening as a result of smooth muscle cell proliferation. The second is thrombus deposition, and this is associated with narrowing and occlusion of the vessels. Although gamma globulin may ameliorate the acute viral infection that is associated with the onset of Kawasaki's disease, it is difficult to determine how it may affect later thrombotic or occlusive events that develop in established postinflammatory aneurysms. Splenic artery aneurysms occurring in children with portal hypertension is a novel event. At the University of Michigan 10% of adults with portal hypertension significant enough to be associated with varices, had concurrent splenic artery macroaneurysms. Many of these patients are candidates for liver transplantation. We would classify these lesions among those caused by arterial dysplasia (group VII). In adults they are invariably associated with dysplasia of the splenic vessels. Liver transplantation may play an important role in the natural history of these aneurysms. Steroids, as part of an antirejection protocol, may diminish elastin or collagen in the aneurysm wall and increase the risk of rupture. Pediatric arterial aneurysms are very rare. There are many similar pathologic changes in our proposed classes, and one could make a case for having fewer classes by combining those exhibiting similar abnormalities, such as Kawasaki's disease and autoimmune diseases. However, major differences in their clinical manifestations led us to classify them separately. In the future, with better definition of the exact genetic and inflammatory disorders that underlie many of these lesions, there may be further subdivisions. The present classification is based on a reasonable analysis of our current knowledge of the pathologic and clinical differences among these unusual aneurysms.