Neuromusc. Disord., Vol. 2, No. 2, pp. 125 135, 1992 Printed in Great Britain
0960-8966/92 $5.00 + 0.00 ©1992 Pergamon Press Ltd
MELAS: AN O R I G I N A L CASE AND CLINICAL CRITERIA FOR DIAGNOSIS MICHIOHIRANO,*~"ENZORICO,* M. RICHARDKOENIGSBERGER,IIRICHARDDEFENDINI,~STEVENG. PAVLAKIS,¶ DARRYLC. DEVIvo,*§ SALVATOREDIMAuRO* and LEWISP. ROWLAND* Departments of *Neurology, :~Pathology(Neuropathology), and §Pediatrics, H. Houston Merritt Clinical Research Center for Muscular Dystrophy and Related Diseases, Columbia-PresbyterianMedical Center, New York, New York; and LIDepartment of Neurosciences, University of Medicine and Dentistry of New Jersey, Newark, New Jersey; and ¶Departments of Neurology and Pediatrics, Cornell Medical Center, New York, U.S.A. (Received 4 February 1992; revised 27 April 1992; accepted 6 May 1992)
describe the full history and postmortem findings in one of the first identified cases of mitochondrial encephalomyopathy with stroke-like episodes (MELAS). To clarify diagnostic criteria, we analyzed 69 reported cases. The syndrome should be suspected by the following three invariant criteria: (1) stroke-like episode before age 40 yr; (2) encephalopathy characterized by seizures, dementia, or both; and (3) lactic acidosis, ragged-red fibers (RRF), or both. The diagnosis may be considered secure if there are also at least two of the following: normal early development, recurrent headache, or recurrent vomiting. There are incomplete syndromes in relatives of patients with the full syndrome and incomplete syndromes might also be encountered in sporadic cases. Some MELAS patients have features of the Kearns-Sayre syndrome (KSS) or myoclonic epilepsy with ragged-red fibers (MERRF), but none had the full KSS syndrome. In partial or confusing cases, analysis of mitochondrial DNA (mtDNA) may point to the correct diagnosis; however, not all patients with clinical MELAS have had the typical mtDNA point mutation and some patients with the mutation have clinical syndromes other than MELAS. Abstract--We
Key words: Mitochondria, mitochondrial DNA, encephalomyopathy, mitochondrial myopathy,
stroke, migraine, headache, MELAS, lactic acidosis, dementia, mental retardation, seizure, ragged-red fiber. INTRODUCTION Mitochondrial encephalomyopathies are manifest by diverse symptoms and signs, most of which can be grouped into distinct syndromes. Analysis of mitochondrial D N A ( m t D N A ) has uncovered distinct mutations in each of the major syndromes. Deletions of m t D N A seem to be restricted to patients with either the K e a r n s Sayre syndrome (KSS), or progressive external ophthalmoplegia (PEO). In contrast, point mutations of m t D N A have been found in five other syndromes: mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) [1]; Leber's hereditary optic neuropathy ( L H O N ) [2]; myoclonus epilepsy with ragged-red fibers ( M E R F F ) [3]; a cardiomyop a t h y - m y o p a t h y syndrome [4]; and neuropathy, ataxia and retinitis pigmentosa (NARP) [5].
tAuthor to whom correspondenceshould be addressed at: Neurological Institute, Columbia-PresbyterianMedical Center, 710 West 168th Street, New York, NY 10032-2603, U.S.A.
In about 86% of M E L A S cases, the mutation is an A-to-G transition in a mtDNA-encoded transfer RNA, t R N A Leu~uUR) at base pair (bp) 3243 [1, 6-9]. A second t R N A Leu~uoR)mutation at bp 3271 has been found in some, but not all, of the M E L A S patients lacking the 3243 bp mutation [10]. Identification of a m t D N A point mutation, therefore, becomes another criterion to diagnose MELAS. The presence of a molecular genetic defect is not independently sufficient to define this syndrome, because not all patients with the M E L A S phenotype have the same mutation [1, 6-10], and furthermore, not all people with the same m t D N A mutation have the same clinical features. We believe that M E L A S exists as a distinct clinical syndrome that needs to be clearly defined based upon the known cases. To start this analysis, we have reviewed all of the clinically reported cases of M E L A S to tabulate the frequency of specific symptoms and signs. As an example, we provide the complete history and postmortem findings in one of the original cases. In 1976, Koenigsberger et al. [11] described a 5-yr-old girl with a symptomatic 125
126
M. HIRANO et al.
myopathy, ragged-red fibers in muscle, and lactic acidosis. Later, she had seizures that included cerebral blindness and there were stroke-like episodes of hemianopsia and hemiparesis. This experience focused our attention on a then-new syndrome which, at a meeting in 1982 [12] we called "mitochondrial encephalopathy with lactic acidosis" or MELA. By that time, there
Table I. Oxidation of radioactive substrates by muscle homogenate in nanomoles ~4CO2min- ~g Substrate I-~4C-Palmitate 2-~4C-Pyruvate UJ4C-Glucose 3-~4C-Hydroxybutyrate
Patient
Controls
1.1 0.1 0.2 0.08
5.44 46.73 40.65 7.30
5: 1.68 (12) 5: 9.45 (10) 5:17.67 (I t) 5: 2.72 (10)
Number of controls is in parentheses.
Table 2. Mitochondrial enzymes in human muscle extract Patient Cytochrome c oxidase*
1.23
Succinate~ytochrome c reductase*
0.52
NADH-cytochrome c reductase*
3.46
Citrate synthetase3"
Controls 2.50 5:0.50 (35; 1.76-3.74) 1.08 ± 0.41 (26; 0.42-1.84) 3.38 ± 1.33 (31; 1.82-6.22) 8.81 ± 0.54 (28; 4.12 16.50) 1.84 5:0.54 (28; 1.05-2.90)
10.29
Carnitine acetyltransferase:~
8.37
All biopsies from vastus lateralis. *Activities expressed as/Jmole substrate reduced or oxidized min- ~g ~protein, tActivities expressed in ,umole formed min- ~g-~; and :~nmol formed min ~g- ~. Control values :t: S.D. with numbers of controls and ranges in parentheses.
Table 3. Clinical features of 69 cases of MELAS Sign/symptom
Present
Recorded Percentage
(1) Cardinal mani festation Exercise intolerance Onset < age 40 Stroke Ragged-red fibers Seizures Lactic acidosis Normal early development
31 66 65 60 61 60 49
31 66 66 62 65 66 54
100 100 98 97 94 91 91
(2) Frequent manifestations Dementia Limb weakness Onset < age 20 Short stature Hemiparesis Hemianopsia Headache Nausea, vomiting Hearing loss Learning disability CSF protein >45
44 49 55 49 47 35 33 41 34 28 16
49 56 66 61 59 46 45 56 48 47 31
90 88 83 80 80 76 73 73 7I 60 52
(3) Other manifestations Basal ganglia calcification* Myoclonus Cerebellar signs Family history Episodic coma Optic atrophy Congestive heart failure Wolff-Parkinson-White Pigmentary retinopathy PEO Cardiac conduction block CSF protein > 100 Diabetes mellitus Impaired sensation
24 18 17 14 9 8 8 6 7 7 3 1 1 1
62 61 63 54 46 42 51 43 61 66 42 30 36 44
39 30 26 26 20 19 16 14 II 11 7 3 3 2
*By CT scan.
MELAS: Original Case and Diagnosis Criteria had been reports of nine similar cases, including two that had been published in 1975 [13, 14], so that our original case was not the first one. In 1984, the acronym was extended to MELAS to include the stroke-like episodes [15]. There are now 69 reported cases [11-57]. Ironically, our original case has not yet been described fully.
DESCRIPTION OF THE PATIENT
This girl was born after a normal pregnancy and delivery. She walked at 1 yr. Early development was normal, but weakness of the legs was apparent at 2 yr when she had difficulty climbing stairs. There was no family history of consanguinity or neurological disease. One younger brother and one older sister were normal; her parents were normal on examination. At 5 yr, examination revealed short stature (92 cm) and low weight (15 kg), both below the third percentile. Cognitive function was appropriate for the age. There was mild proximal weakness with a Gowers sign; tendon reflexes and other findings were normal. At 5½ yr, after strenuous exercise, she lost consciousness for 30 min. She also had multiple episodes of dimmed vision lasting a few minutes. Because there were high venous concentrations of lactate (100 mg dl t) and pyruvate (5 mg dl-l), she was treated with thiamine with no effect. At 6 yr, episodes of right-sided paresthesias after physical exertion lasted 30-60 min and were followed by blindness. She was not examined during an attack, but one episode was followed by a generalized tonic--clonic seizure, and phenobarbital therapy was started. Postictally, there was a right hemiparesis that improved after 3 days. A second right focal seizure was followed by a hemiparesis for 5 days. Phenobarbital dosage was increased and sodium bicarbonate added. Oral methylene blue therapy was started and the bicarbonate was discontinued without a change in the lactate concentration. After another generalized seizure with blindness, methylene blue was discontinued. The loss of vision was thought to be cortical in origin because pupillary reactions to light and fundoscopic examination were normal. Audiogram was normal at age 5, but showed neurosensory hearing loss at age 9 yr. At 6 ½yr, pneumonia and congestive heart failure were treated with antibiotics and digoxin. Due to the increasing frequency of episodes, carbamazepine therapy was started. At 7 yr, Lcarnitine (100 mg kg -t day -t) was given by
127
mouth for 5 months without clinical or biochemical improvement. The disorder continued to progress; at 9 yr, she was severely demented and deaf, speaking in only short phrases. Physostigmine was given without effect. Highdose vitamin C (600 mg day-1) also failed and prednisolone (2 mg kg -1 day ~) was similarly ineffective. At 10 yr, she died in congestive heart failure. She never had pigmentary retinopathy, ophthalmoplegia, or cerebellar syndrome, and repeated electrocardiograms did not show conduction block.
Special studies Brain CT at age 7 yr showed mild cerebellar atrophy. Venous blood was obtained without a tourniquet to measure the venous content of lactate before and after she ran 60 m; there was no change in lactate content, but the baseline measurement was greater than four times the upper limit of normal. Using methods described elsewhere, biochemical studies of mitochondrial functions were assessed [15, 58]. Oxidation of radioactive substrate was reduced in muscle homogenate, but was normal in leucocytes (Table 1). All mitochondrial enzyme activities were lower than controls in a nonspecific pattern (Table 2). Pyruvate dehydrogenase activity was normal [11, 15]. Mitochondrial DNA was extracted from blood of the patient's mother; brother, 17 yr old; and two sisters, 13 and 23 yr old. The brother was affected, with short stature, mental retardation and hearing loss. The female members of the family were clinically unaffected. However, using our laboratory methods [7] all four of these relatives had abnormal m t D N A in blood ranging from 14% in the brother to 59% in the mother. The younger sister had 55% mutated D N A while the older sister had 15%. D N A studies could not be performed in the proposita.
Postmortem findings in brain and spinal cord At autopsy, mild atrophy of the cerebral hemispheres was attributed to countless small cortical infarcts. The occipital and posterior portions of the temporal lobes were more extensively affected than the anterior two-thirds of the cerebrum, but virtually all convolutions showed microscopic injury. In sharp contrast to the parahippocampal gyrus, Ammon's horn was spared. The precalcarine visual pathways were well preserved. There were no focal lesions in any
128
M. HIRANO et al. Table 4. Initial clinical manifestation
Age of onset
0960-8966/92 $5.00 + 0.00 ©1992 Pergamon Press Ltd
MELAS: AN O R I G I N A L CASE AND CLINICAL CRITERIA FOR DIAGNOSIS MICHIOHIRANO,*~"ENZORICO,* M. RICHARDKOENIGSBERGER,IIRICHARDDEFENDINI,~STEVENG. PAVLAKIS,¶ DARRYLC. DEVIvo,*§ SALVATOREDIMAuRO* and LEWISP. ROWLAND* Departments of *Neurology, :~Pathology(Neuropathology), and §Pediatrics, H. Houston Merritt Clinical Research Center for Muscular Dystrophy and Related Diseases, Columbia-PresbyterianMedical Center, New York, New York; and LIDepartment of Neurosciences, University of Medicine and Dentistry of New Jersey, Newark, New Jersey; and ¶Departments of Neurology and Pediatrics, Cornell Medical Center, New York, U.S.A. (Received 4 February 1992; revised 27 April 1992; accepted 6 May 1992)
describe the full history and postmortem findings in one of the first identified cases of mitochondrial encephalomyopathy with stroke-like episodes (MELAS). To clarify diagnostic criteria, we analyzed 69 reported cases. The syndrome should be suspected by the following three invariant criteria: (1) stroke-like episode before age 40 yr; (2) encephalopathy characterized by seizures, dementia, or both; and (3) lactic acidosis, ragged-red fibers (RRF), or both. The diagnosis may be considered secure if there are also at least two of the following: normal early development, recurrent headache, or recurrent vomiting. There are incomplete syndromes in relatives of patients with the full syndrome and incomplete syndromes might also be encountered in sporadic cases. Some MELAS patients have features of the Kearns-Sayre syndrome (KSS) or myoclonic epilepsy with ragged-red fibers (MERRF), but none had the full KSS syndrome. In partial or confusing cases, analysis of mitochondrial DNA (mtDNA) may point to the correct diagnosis; however, not all patients with clinical MELAS have had the typical mtDNA point mutation and some patients with the mutation have clinical syndromes other than MELAS. Abstract--We
Key words: Mitochondria, mitochondrial DNA, encephalomyopathy, mitochondrial myopathy,
stroke, migraine, headache, MELAS, lactic acidosis, dementia, mental retardation, seizure, ragged-red fiber. INTRODUCTION Mitochondrial encephalomyopathies are manifest by diverse symptoms and signs, most of which can be grouped into distinct syndromes. Analysis of mitochondrial D N A ( m t D N A ) has uncovered distinct mutations in each of the major syndromes. Deletions of m t D N A seem to be restricted to patients with either the K e a r n s Sayre syndrome (KSS), or progressive external ophthalmoplegia (PEO). In contrast, point mutations of m t D N A have been found in five other syndromes: mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) [1]; Leber's hereditary optic neuropathy ( L H O N ) [2]; myoclonus epilepsy with ragged-red fibers ( M E R F F ) [3]; a cardiomyop a t h y - m y o p a t h y syndrome [4]; and neuropathy, ataxia and retinitis pigmentosa (NARP) [5].
tAuthor to whom correspondenceshould be addressed at: Neurological Institute, Columbia-PresbyterianMedical Center, 710 West 168th Street, New York, NY 10032-2603, U.S.A.
In about 86% of M E L A S cases, the mutation is an A-to-G transition in a mtDNA-encoded transfer RNA, t R N A Leu~uUR) at base pair (bp) 3243 [1, 6-9]. A second t R N A Leu~uoR)mutation at bp 3271 has been found in some, but not all, of the M E L A S patients lacking the 3243 bp mutation [10]. Identification of a m t D N A point mutation, therefore, becomes another criterion to diagnose MELAS. The presence of a molecular genetic defect is not independently sufficient to define this syndrome, because not all patients with the M E L A S phenotype have the same mutation [1, 6-10], and furthermore, not all people with the same m t D N A mutation have the same clinical features. We believe that M E L A S exists as a distinct clinical syndrome that needs to be clearly defined based upon the known cases. To start this analysis, we have reviewed all of the clinically reported cases of M E L A S to tabulate the frequency of specific symptoms and signs. As an example, we provide the complete history and postmortem findings in one of the original cases. In 1976, Koenigsberger et al. [11] described a 5-yr-old girl with a symptomatic 125
126
M. HIRANO et al.
myopathy, ragged-red fibers in muscle, and lactic acidosis. Later, she had seizures that included cerebral blindness and there were stroke-like episodes of hemianopsia and hemiparesis. This experience focused our attention on a then-new syndrome which, at a meeting in 1982 [12] we called "mitochondrial encephalopathy with lactic acidosis" or MELA. By that time, there
Table I. Oxidation of radioactive substrates by muscle homogenate in nanomoles ~4CO2min- ~g Substrate I-~4C-Palmitate 2-~4C-Pyruvate UJ4C-Glucose 3-~4C-Hydroxybutyrate
Patient
Controls
1.1 0.1 0.2 0.08
5.44 46.73 40.65 7.30
5: 1.68 (12) 5: 9.45 (10) 5:17.67 (I t) 5: 2.72 (10)
Number of controls is in parentheses.
Table 2. Mitochondrial enzymes in human muscle extract Patient Cytochrome c oxidase*
1.23
Succinate~ytochrome c reductase*
0.52
NADH-cytochrome c reductase*
3.46
Citrate synthetase3"
Controls 2.50 5:0.50 (35; 1.76-3.74) 1.08 ± 0.41 (26; 0.42-1.84) 3.38 ± 1.33 (31; 1.82-6.22) 8.81 ± 0.54 (28; 4.12 16.50) 1.84 5:0.54 (28; 1.05-2.90)
10.29
Carnitine acetyltransferase:~
8.37
All biopsies from vastus lateralis. *Activities expressed as/Jmole substrate reduced or oxidized min- ~g ~protein, tActivities expressed in ,umole formed min- ~g-~; and :~nmol formed min ~g- ~. Control values :t: S.D. with numbers of controls and ranges in parentheses.
Table 3. Clinical features of 69 cases of MELAS Sign/symptom
Present
Recorded Percentage
(1) Cardinal mani festation Exercise intolerance Onset < age 40 Stroke Ragged-red fibers Seizures Lactic acidosis Normal early development
31 66 65 60 61 60 49
31 66 66 62 65 66 54
100 100 98 97 94 91 91
(2) Frequent manifestations Dementia Limb weakness Onset < age 20 Short stature Hemiparesis Hemianopsia Headache Nausea, vomiting Hearing loss Learning disability CSF protein >45
44 49 55 49 47 35 33 41 34 28 16
49 56 66 61 59 46 45 56 48 47 31
90 88 83 80 80 76 73 73 7I 60 52
(3) Other manifestations Basal ganglia calcification* Myoclonus Cerebellar signs Family history Episodic coma Optic atrophy Congestive heart failure Wolff-Parkinson-White Pigmentary retinopathy PEO Cardiac conduction block CSF protein > 100 Diabetes mellitus Impaired sensation
24 18 17 14 9 8 8 6 7 7 3 1 1 1
62 61 63 54 46 42 51 43 61 66 42 30 36 44
39 30 26 26 20 19 16 14 II 11 7 3 3 2
*By CT scan.
MELAS: Original Case and Diagnosis Criteria had been reports of nine similar cases, including two that had been published in 1975 [13, 14], so that our original case was not the first one. In 1984, the acronym was extended to MELAS to include the stroke-like episodes [15]. There are now 69 reported cases [11-57]. Ironically, our original case has not yet been described fully.
DESCRIPTION OF THE PATIENT
This girl was born after a normal pregnancy and delivery. She walked at 1 yr. Early development was normal, but weakness of the legs was apparent at 2 yr when she had difficulty climbing stairs. There was no family history of consanguinity or neurological disease. One younger brother and one older sister were normal; her parents were normal on examination. At 5 yr, examination revealed short stature (92 cm) and low weight (15 kg), both below the third percentile. Cognitive function was appropriate for the age. There was mild proximal weakness with a Gowers sign; tendon reflexes and other findings were normal. At 5½ yr, after strenuous exercise, she lost consciousness for 30 min. She also had multiple episodes of dimmed vision lasting a few minutes. Because there were high venous concentrations of lactate (100 mg dl t) and pyruvate (5 mg dl-l), she was treated with thiamine with no effect. At 6 yr, episodes of right-sided paresthesias after physical exertion lasted 30-60 min and were followed by blindness. She was not examined during an attack, but one episode was followed by a generalized tonic--clonic seizure, and phenobarbital therapy was started. Postictally, there was a right hemiparesis that improved after 3 days. A second right focal seizure was followed by a hemiparesis for 5 days. Phenobarbital dosage was increased and sodium bicarbonate added. Oral methylene blue therapy was started and the bicarbonate was discontinued without a change in the lactate concentration. After another generalized seizure with blindness, methylene blue was discontinued. The loss of vision was thought to be cortical in origin because pupillary reactions to light and fundoscopic examination were normal. Audiogram was normal at age 5, but showed neurosensory hearing loss at age 9 yr. At 6 ½yr, pneumonia and congestive heart failure were treated with antibiotics and digoxin. Due to the increasing frequency of episodes, carbamazepine therapy was started. At 7 yr, Lcarnitine (100 mg kg -t day -t) was given by
127
mouth for 5 months without clinical or biochemical improvement. The disorder continued to progress; at 9 yr, she was severely demented and deaf, speaking in only short phrases. Physostigmine was given without effect. Highdose vitamin C (600 mg day-1) also failed and prednisolone (2 mg kg -1 day ~) was similarly ineffective. At 10 yr, she died in congestive heart failure. She never had pigmentary retinopathy, ophthalmoplegia, or cerebellar syndrome, and repeated electrocardiograms did not show conduction block.
Special studies Brain CT at age 7 yr showed mild cerebellar atrophy. Venous blood was obtained without a tourniquet to measure the venous content of lactate before and after she ran 60 m; there was no change in lactate content, but the baseline measurement was greater than four times the upper limit of normal. Using methods described elsewhere, biochemical studies of mitochondrial functions were assessed [15, 58]. Oxidation of radioactive substrate was reduced in muscle homogenate, but was normal in leucocytes (Table 1). All mitochondrial enzyme activities were lower than controls in a nonspecific pattern (Table 2). Pyruvate dehydrogenase activity was normal [11, 15]. Mitochondrial DNA was extracted from blood of the patient's mother; brother, 17 yr old; and two sisters, 13 and 23 yr old. The brother was affected, with short stature, mental retardation and hearing loss. The female members of the family were clinically unaffected. However, using our laboratory methods [7] all four of these relatives had abnormal m t D N A in blood ranging from 14% in the brother to 59% in the mother. The younger sister had 55% mutated D N A while the older sister had 15%. D N A studies could not be performed in the proposita.
Postmortem findings in brain and spinal cord At autopsy, mild atrophy of the cerebral hemispheres was attributed to countless small cortical infarcts. The occipital and posterior portions of the temporal lobes were more extensively affected than the anterior two-thirds of the cerebrum, but virtually all convolutions showed microscopic injury. In sharp contrast to the parahippocampal gyrus, Ammon's horn was spared. The precalcarine visual pathways were well preserved. There were no focal lesions in any
128
M. HIRANO et al. Table 4. Initial clinical manifestation
Age of onset
