54
sphenoidal adenomectomy. Complete remission of Cushing’s disease was seen, apart from osteoporosis. The patient resumed work on her farm and was well. She took hydrocortisone (20-30 mg daily) only when she was stressed. In September, 1990, serum cortisol concentration and 24-h urinary17-OHCS excretion were at the lower normal range. We believe that immunosuppression due to endogenous high blood cortisol was the main factor predisposing our patient to altemariosis. This infection is also an occupational hazard in farmers. Mitotane is not an antifungal drug, so we believe that alternarioris resolved because of the inhibitory effect of mitotane on steroidogenesis. A direct action of mitotane on A alternata infection seems
unlikely.
Department of Endocrinology, Centre of Postgraduate Medical Education, 01-809 Warsaw, Poland
A. A. KASPERLIR-ZALUSRA
of
Department Dermatology, Academy of Medicine,
SABINA BIELUŃSKA
Warsaw
1. Aznar R, Margil J, Puig de la Bellacase J, et al Cutaneous alternariosis ketocenazole Lancet 1989, i. 667-68
responding to
Peritonitis due to
vancomycin-resistant Staphylococcus epidermidis
SIR,-Vancomycin and teicoplanin are glycopeptide antibiotics active against most species of gram-positive bacteria. Vancomycin is often the antibiotic of choice for infections due to coagulasenegative staphylococci, especially if the organisms are resistant to methicillin. However, gram-positive bacteria resistant to glycopeptide antibiotics are emerging. We report a case of continuous ambulatory peritoneal dialysis (CAPD) peritonitis due to Staphylococcus epidermidis resistant to vancomycin and teicoplanin. A 51-year-old man, treated with CAPD for end-stage renal failure, presented with symptoms of CAPD peritonitis. He was given intraperitoneal vancomycin (25 mg/1) and gentamicin (4 mg/1). Response was poor, and culture of the CAPD fluid yielded S epidermidis (’API Staph’, BioMerieux, France). The isolate was non-typable with phage (Staphylococcus Reference Laboratory, Public Health Laboratory Service, UK). The organism was also isolated from the Tenchkoff cannula exit site. Initial antimicrobial sensitivity testing by the breakpoint method showed the isolate to be resistant to vancomycin (minimum inhibitory concentration [MIC] >4 mg/1). On subsequent MIC testing the isolate was resistant to vancomycin (MIC = 16 mg/1), > 32 teicoplanin (MIC > 16 mg/1), gentamicin mg/1), tobramycin (MIC 32 mg/1), and trimethoprim (MIC > 8 mg/l, and sensitive to methicillin, erythromycin, fusidic acid, and tetracycline. The MICs for vancomycin and teicoplanin were not affected by presence or absence in the medium (’Isosensitest’ agar) of 2% lysed blood. The patient was started on oral erythromycin and his symptoms resolved slowly. However, he was readmitted 3 weeks later with CAPD peritonitis; cloudy bags yielded vancomycin-resistant S epiderrraidis. Swabs of the nose, axilla, and perineum taken during both admissions failed to grow vancomycinresistant S epidermidis. During the second admission, the Tenchkoff cannula, which was the probable focus of infection, was removed and the patient was started on haemodialysis. The patient had had ten previous episodes in 3 years of CAPD peritonitis caused by coagulase-negative staphylococci. All episodes had been treated with intraperitoneal vancomycin. It is possible that repeated exposure to vancomycin caused emergence of resistance to this antibiotic. Although the genetic and biochemical basis for resistance to vancomycin and teicoplanin in this isolate is not known, it is unlikely to be plasmid-mediated, because plasmids could not be detected by repeated analysis in 0’7-0’8% agarose gels. That the isolate seemed to be sensitive to vancomycin and teicoplanin by Stokes’ methodz (30 µg discs) with NCTC 6571 as control is worrying; this was seen with both isosensitest and ’Diagnostic Sensitivity Test’ agar with and without lysed horse blood. It is possible, therefore, that similar strains might not be
(MIC
detected in laboratories that use only this method for routine testing. 5 µg vancomycin discs gave a zone size of 2 mm for the patient isolate and 5 mm for NCTC 6571, indicating resistance. Vancomycin resistance of the order reported here has been
reported previously in coagulase-negative staphylococci,3,4 although susceptibility to teicoplanin was not determined. Teicoplanin-resistant, vancomycin-susceptible, coagulase-negative staphylococci have also been described,5,6 as has CAPD peritonitis caused by a strain of S haemolyticus that was initially only teicoplanin-resistant (MIC = 16 mg/1) but developed vancomycin resistance (MIC =8 mg/1).’ It is possible that glycopeptideresistant, coagulase-negative staphylococci will be seen with increasing frequency, particularly if such infections are treated with repeated courses of vancomycin. Additionally, the observation of probable cross-colonisation of CAPD patients with ciprofloxacinresistant coagulase-negative staphylococci8 suggests that a similar cross-colonisation might occur with glycopeptide-resistant organisms. Laboratories may need to review methods for testing susceptibility to vancomycin, particularly if they examine specimens from patients exposed to repeated courses of vancomycin. Such strains may be more readily detected by breakpoint testing at 4 mg/1’ or 5 pg vancomycin discs. The poor clinical response to intraperitoneal vancomycin therapy in our patient suggests that low-level resistance is important, even though the therapeutic concentration used (25 mg vancomycin per litre dialysate) exceeded the in-vitro MIC. We thank Dr C. Brown for permission to report on this patient; Dr R. R. and Dr J. F. Richardson for confirming the identity of the isolate; and Ms Marina Warner for the Stokes test.
Marples
Public Health Laboratory, Northern General Hospital, Sheffield
D. SANYAL
Division of Hospital Infection, Central Public Health Laboratory, London NW9 5HT, UK
A. P. JOHNSON R. C. GEORGE B. D. COOKSON
Department of Renal Medicine, Northern General Hospital, Sheffield
A.
J. WILLIAMS
1 Johnson AP, Uttley AHC, Woodford N, George RC. Resistance to vancomycin and teicoplanin an emerging clinical problem Clin Microbiol Rev 1990; 3: 280-91. 2 Stokes EJ, Ridgway GL. Clinical microbiology 6th ed. London Edward Arnold, 1987 204-21. 3 Cherubin CE, Corrado
ML, Sierra MF, et al Susceptibility of gram-positive cocci to antibiotics, including cefotaxime, moxalactam and N-formimidoyl thienamycin Antimicrob Agents Chemother 1981, 20: 553-55. various
CU, Miller H. Clinical and microbiologic aspects of serious infections caused by Staphylococcus epidermidis. ScandJ Infect Dis 1983; 15: 347-60 Arioli V, Pallanza R Teicoplanin-resistant coagulase negative staphylococci Lancet
4. Tuazon 5
1987, i. 39 6 Wilson APR, O’Hare MD,
=
7. 8.
Felmingham D, Gruneberg RN Teicoplanin-resistant coagulase-negative staphylococcus Lancet 1986, ii: 973 Schwalbe RS, Stapleton JT, Gilligan PH Emergence of vancomycin resistance in coagulase-negative staphylococci N Engl J Med 1987; 316: 927-31 Dryden MS, Ludlam HA, Phillips I. 4-Quinolone-resistant staphylococci J Antumcrob Chemother 1990; 26: 448-49
9
Report by a Working Party of the British Society for Antimicrobial Chemotherpay Breakpoints in in-vitro antibiotic sensitivity testing J Antimicrob Chemother 1988, 21: 701-10
Determinants of
pancreatic and pulmonary cystic fibrosis
status of
SIR,-In their study of pancreatic and pulmonary status among siblings with cystic fibrosis (CF), Dr Santis and colleagues (Nov 3, p 1081) conclude that genetic factors are more important than non-genetic factors in the determination of severity of disease in pancreas and lungs, and that the genetic factors are independent of each other. They suggest that genes at loci other than that for the CF transmembrane conductance regulator (CFTR) might be responsible. I feel that there is no need to invoke other genetic contributions, and that Santis et al too readily dismiss the role of "non-genetic" factors, having examined only a few of these. Important determining factors that are difficult to measure include the adequacy of care given in early life, as well as later, and the degree of compliance with treatment regimens. Cross-infection with virulent
55
organisms within families could also be important but is not genetically determined. Such variables affect pulmonary, but not pancreatic, status. The evidence produced by Santis and colleagues, and by others,’ is consistent with the view that the &Dgr;F508 mutation is probably associated with severe disease in both the pancreas and the lungs. Our own preliminary observations suggest that other mutations affecting exon 10 should be regarded as equivalent to &Dgr;F508 (O’Rawe A, Dodge JA, unpublished). Not only do severe involvement of the lungs and the pancreas in CF tend to occur together, but also there is evidence that patients with milder pancreatic disease have lower sweat electrolyte valuessuggesting that mild and severe CF variants are not organ-specific. We should not be surprised at the fact that not all patients with a certain genetic abnormality behave in precisely the same way. Destruction of the exocrine pancreas is an end result of disordered physiology, in which duct obstruction occurs and is associated with chronic pancreatitis. The extent of pancreatic damage at particular ages will depend both on the underlying severity of the genetic disorder and on the location and number of ductules that happen to be blocked. All the genetic ingredients may be present but the rate of progress of the condition will depend on random, non-genetic factors within the organ itself. In infantile hypertonic pyloric stenosis, which also has a genetically determined predisposition, I have seen identical twins who were apparently discordant, the "unaffected" infant having radiologial evidence of pyloric hypertrophy but no vomiting. Similar cases have been recorded before. These infants shared both genes and environment. I concluded that individual physiological variables determined whether actual or only potential obstruction occurred.3 In biological systems it is not always reasonable to expect a uniform rate of progress among individuals. My point may be important because one consequence of accepting that outcomes in CF are entirely determined by gene mutations could be a fatalistic approach to management, in the belief that the genes would have the last word. The documented improvement in prognosis during the past two decades’ proves that progress can be substantially modified by non-genetic factors. Nuffield Department of Child Health, Queen’s University of Belfast, Institute of Clinical Science, Belfast BT12 6BJ, UK
J. A. DODGE
1. Gaskin K, Gurwitz D, Dune P, et al. Improved respiratory prognosis m patients with cystic fibrosis with normal fat absorption J Pediatr 1982; 100: 857-62. 2 Davis PB, Hubbard VS, di Sant’Agnese PA Low sweat electrolytes in a patient with cystic fibrosis. Am J Med 1980, 69: 643-46 3 Dodge JA. Genetics of hypertrophic pyloric stenosis. Clinics Gastroenterol 1973, 2: 523-38. 4 British Paediatric Association Working Party on Cystic Fibrosis. Cystic fibrosis in the United Kingdom 1977-85: an improving picture Br Med J 1988, 297: 1599-602.
Abnormal
neonatal
frequency of &Dgr;F508 mutation in transitory hypertrypsinaemia
SIR,—As pointed out by Dumur et al’ heterozygosity for the cystic fibrosis (CF) &Dgr;F508 mutation is more frequent than expected2 in adults with chronic bronchial hypersecretion. This suggests that heterozygotes for CF may have some mild forms of the disease. Newborn babies with CF have abnormally high levels of immunoreactive trypsin (IRT) in serum, which is the basis for a screening test.3 Using the dried blood spots collected for CF screening we looked at carrier frequencies of dF 508 mutation in babies with mildly raised IRT concentrations. In our CF screening programme 08% of newborn babies have IRT concentrations of 600 µg/l on the 4th day of life, 0-3% being above 800 µg/l (Behring units).’ In the CF population 95% of neonates have an IRT above 800 p.g/1 on day 4 and above 600 I1g/1 on day 21, 5% of CF neonates having a normal IRT (false negative). Less than 1 in 15 000 non-CF babies have the same IRT pattern as babies with CF. From January to September, 1990, 28 000 babies were screened; 149 had an IRT on day 4 of 600 µg/l and below 600
µg/l on day 21. We identified 9 &Dgr;F508 heterozygotes, who were presumed not to have CF since, for ethical reasons, they would not
be sweat-tested in the absence of persistent hypertrypsinaemia. The incidence of CF in our region is 1 in 3150 with a carrier frequency of CF of 1 in 28. In our CF population, the frequency of .’1F5o8 is slightly lower than the 70% usually reported for France,’ with an expected incidence of the .’1F 508 heterozygotes of 1 in 42. The frequency of .’1F 508 mutation reported here in a restricted population (9 in 149) is significantly higher (p < 0 01; corrected chi square) than expected. These .’1F 508 heterozygotes may have a predisposition to some mild biological abnormalities as early as the first days of life.
Supported by Association Française de Lutte contre la Mucoviscidose. We thank Dr C. Ferec (Brest) for advice. Radioisotope Service, CHRU de Caen, 14033 Caen, France
DOMINIQUE LAROCHE GEORGES TRAVERT
V, Lafitte JJ, Gervais R, et al. Abnormal distribution of cystic fibrosis &Dgr;F508 allele in adults with chronic bronchial hypersecretion. Lancet 1990, 335: 1340. Kerem BS, Rommens JM, Buchanan JA, et al. Identification of the cystic fibrosis gene: genetic analysis. Science 1989, 245: 1073-80 Crossley JR, Elliott RB, Smith PA. Dried blood spot screening for cystic fibrosis in the newborn. Lancet 1979, i: 472-74 Travert G, Duhamel JF Neonatal screening for cystic fibrosis using trypsin radioimmunoassay in blood Arch Fr Pédiatr 1983; 40: 295-98 Cystic Fibrosis Genetic Analysis Consortium. Worldwide survey of the &Dgr;F508 mutation. Am J Hum Genet 1990, 47: 354-59.
1 Dumur
2 3 4 5
&bgr;(A4)-amyloid protein and parkinsoniandementia complex of Guam SIR,—Intracellular neurofibrillary tangles are a common feature of Alzheimer’s disease (AD), older patients with Down’s syndrome, dementia pugilistica ("punch-drunk syndrome" of boxers) and the parkinsonian-dementia complex amyotrophic lateral sclerosis (PDG/ALS) that is endemic among the Chamorro people of Guam. The tangles in these disorders contain similar antigenic components,’ perhaps pointing to a common pathogenesis. The other major characteristic lesions associated with AD, the extracellular &bgr;(A4)-amyloid plaques, are thought to be absent in boxer’s dementia and PDG/ALS. However, immunohistochemistry using antibodies to the &bgr;(A4)-amyloid protein component of plaque cores has revealed "diffuse" amyloid plaques in the brains of AD, Down’s syndrome, and to some extent, normal elderly control patients3.4 which are not detectable by conventional stains. We have, to our surprise, found diffuse &bgr;(A4)-amyloid plaques in the brains of boxers with dementia pugilistica.5 We wondered whether these plaques are present in the brains of PDG/ALS patients-a question of special interest in view of the realisation that AD is probably aetiologically heterogeneous6 and that both genetic and environmental factors are implicated. We have screened paraffin-embedded, formalin-fixed sections of temporal lobe tissue from 8 patients with PDG/ALS (6 males and 2 females, aged 33-66 years) using a monoclonal antibody (4D12/2/6) raised against residues 8-17 of the &bgr;-protein. The immunocytochemical techniques are described in detail elsewhere.’ 80% formic acid was used to pretreat the sections for 20 min to increase the antigenicity of the &bgr;-protein, and sections of AD brain were used as positive controls. All the AD control brains had intense staining of the &bgr;-protein deposits throughout the cortical ribbon and to some extent within the white-matter. Little or no trace of &bgr;-protein immunoreactivity was observed in any of the PDG/ALS cases. A limited amount of &bgr;(A4)-amyloid deposition has been observed in two old (> 65 years) PDG/ALS cases;’ however, the degree of deposition was consistent with that commonly found in normal ageing.3 The cause of endemic PDG/ALS in Guam is unknown. Although clustering has been noted within families, no genetic component has yet been isolated, and epidemiological evidence strongly points to an exogenous or environmental caused One hypothesis is that the deficits in mineral metabolism result in the accumulation of calcium and aluminium deposits which may lead to neuronal degradation and neurofibrillary tangle formation.9 Another centres around the neurotoxic cycads in the Chamorro diet.8 The absence of &bgr;-amyloid immunoreactive plaques in
sphenoidal adenomectomy. Complete remission of Cushing’s disease was seen, apart from osteoporosis. The patient resumed work on her farm and was well. She took hydrocortisone (20-30 mg daily) only when she was stressed. In September, 1990, serum cortisol concentration and 24-h urinary17-OHCS excretion were at the lower normal range. We believe that immunosuppression due to endogenous high blood cortisol was the main factor predisposing our patient to altemariosis. This infection is also an occupational hazard in farmers. Mitotane is not an antifungal drug, so we believe that alternarioris resolved because of the inhibitory effect of mitotane on steroidogenesis. A direct action of mitotane on A alternata infection seems
unlikely.
Department of Endocrinology, Centre of Postgraduate Medical Education, 01-809 Warsaw, Poland
A. A. KASPERLIR-ZALUSRA
of
Department Dermatology, Academy of Medicine,
SABINA BIELUŃSKA
Warsaw
1. Aznar R, Margil J, Puig de la Bellacase J, et al Cutaneous alternariosis ketocenazole Lancet 1989, i. 667-68
responding to
Peritonitis due to
vancomycin-resistant Staphylococcus epidermidis
SIR,-Vancomycin and teicoplanin are glycopeptide antibiotics active against most species of gram-positive bacteria. Vancomycin is often the antibiotic of choice for infections due to coagulasenegative staphylococci, especially if the organisms are resistant to methicillin. However, gram-positive bacteria resistant to glycopeptide antibiotics are emerging. We report a case of continuous ambulatory peritoneal dialysis (CAPD) peritonitis due to Staphylococcus epidermidis resistant to vancomycin and teicoplanin. A 51-year-old man, treated with CAPD for end-stage renal failure, presented with symptoms of CAPD peritonitis. He was given intraperitoneal vancomycin (25 mg/1) and gentamicin (4 mg/1). Response was poor, and culture of the CAPD fluid yielded S epidermidis (’API Staph’, BioMerieux, France). The isolate was non-typable with phage (Staphylococcus Reference Laboratory, Public Health Laboratory Service, UK). The organism was also isolated from the Tenchkoff cannula exit site. Initial antimicrobial sensitivity testing by the breakpoint method showed the isolate to be resistant to vancomycin (minimum inhibitory concentration [MIC] >4 mg/1). On subsequent MIC testing the isolate was resistant to vancomycin (MIC = 16 mg/1), > 32 teicoplanin (MIC > 16 mg/1), gentamicin mg/1), tobramycin (MIC 32 mg/1), and trimethoprim (MIC > 8 mg/l, and sensitive to methicillin, erythromycin, fusidic acid, and tetracycline. The MICs for vancomycin and teicoplanin were not affected by presence or absence in the medium (’Isosensitest’ agar) of 2% lysed blood. The patient was started on oral erythromycin and his symptoms resolved slowly. However, he was readmitted 3 weeks later with CAPD peritonitis; cloudy bags yielded vancomycin-resistant S epiderrraidis. Swabs of the nose, axilla, and perineum taken during both admissions failed to grow vancomycinresistant S epidermidis. During the second admission, the Tenchkoff cannula, which was the probable focus of infection, was removed and the patient was started on haemodialysis. The patient had had ten previous episodes in 3 years of CAPD peritonitis caused by coagulase-negative staphylococci. All episodes had been treated with intraperitoneal vancomycin. It is possible that repeated exposure to vancomycin caused emergence of resistance to this antibiotic. Although the genetic and biochemical basis for resistance to vancomycin and teicoplanin in this isolate is not known, it is unlikely to be plasmid-mediated, because plasmids could not be detected by repeated analysis in 0’7-0’8% agarose gels. That the isolate seemed to be sensitive to vancomycin and teicoplanin by Stokes’ methodz (30 µg discs) with NCTC 6571 as control is worrying; this was seen with both isosensitest and ’Diagnostic Sensitivity Test’ agar with and without lysed horse blood. It is possible, therefore, that similar strains might not be
(MIC
detected in laboratories that use only this method for routine testing. 5 µg vancomycin discs gave a zone size of 2 mm for the patient isolate and 5 mm for NCTC 6571, indicating resistance. Vancomycin resistance of the order reported here has been
reported previously in coagulase-negative staphylococci,3,4 although susceptibility to teicoplanin was not determined. Teicoplanin-resistant, vancomycin-susceptible, coagulase-negative staphylococci have also been described,5,6 as has CAPD peritonitis caused by a strain of S haemolyticus that was initially only teicoplanin-resistant (MIC = 16 mg/1) but developed vancomycin resistance (MIC =8 mg/1).’ It is possible that glycopeptideresistant, coagulase-negative staphylococci will be seen with increasing frequency, particularly if such infections are treated with repeated courses of vancomycin. Additionally, the observation of probable cross-colonisation of CAPD patients with ciprofloxacinresistant coagulase-negative staphylococci8 suggests that a similar cross-colonisation might occur with glycopeptide-resistant organisms. Laboratories may need to review methods for testing susceptibility to vancomycin, particularly if they examine specimens from patients exposed to repeated courses of vancomycin. Such strains may be more readily detected by breakpoint testing at 4 mg/1’ or 5 pg vancomycin discs. The poor clinical response to intraperitoneal vancomycin therapy in our patient suggests that low-level resistance is important, even though the therapeutic concentration used (25 mg vancomycin per litre dialysate) exceeded the in-vitro MIC. We thank Dr C. Brown for permission to report on this patient; Dr R. R. and Dr J. F. Richardson for confirming the identity of the isolate; and Ms Marina Warner for the Stokes test.
Marples
Public Health Laboratory, Northern General Hospital, Sheffield
D. SANYAL
Division of Hospital Infection, Central Public Health Laboratory, London NW9 5HT, UK
A. P. JOHNSON R. C. GEORGE B. D. COOKSON
Department of Renal Medicine, Northern General Hospital, Sheffield
A.
J. WILLIAMS
1 Johnson AP, Uttley AHC, Woodford N, George RC. Resistance to vancomycin and teicoplanin an emerging clinical problem Clin Microbiol Rev 1990; 3: 280-91. 2 Stokes EJ, Ridgway GL. Clinical microbiology 6th ed. London Edward Arnold, 1987 204-21. 3 Cherubin CE, Corrado
ML, Sierra MF, et al Susceptibility of gram-positive cocci to antibiotics, including cefotaxime, moxalactam and N-formimidoyl thienamycin Antimicrob Agents Chemother 1981, 20: 553-55. various
CU, Miller H. Clinical and microbiologic aspects of serious infections caused by Staphylococcus epidermidis. ScandJ Infect Dis 1983; 15: 347-60 Arioli V, Pallanza R Teicoplanin-resistant coagulase negative staphylococci Lancet
4. Tuazon 5
1987, i. 39 6 Wilson APR, O’Hare MD,
=
7. 8.
Felmingham D, Gruneberg RN Teicoplanin-resistant coagulase-negative staphylococcus Lancet 1986, ii: 973 Schwalbe RS, Stapleton JT, Gilligan PH Emergence of vancomycin resistance in coagulase-negative staphylococci N Engl J Med 1987; 316: 927-31 Dryden MS, Ludlam HA, Phillips I. 4-Quinolone-resistant staphylococci J Antumcrob Chemother 1990; 26: 448-49
9
Report by a Working Party of the British Society for Antimicrobial Chemotherpay Breakpoints in in-vitro antibiotic sensitivity testing J Antimicrob Chemother 1988, 21: 701-10
Determinants of
pancreatic and pulmonary cystic fibrosis
status of
SIR,-In their study of pancreatic and pulmonary status among siblings with cystic fibrosis (CF), Dr Santis and colleagues (Nov 3, p 1081) conclude that genetic factors are more important than non-genetic factors in the determination of severity of disease in pancreas and lungs, and that the genetic factors are independent of each other. They suggest that genes at loci other than that for the CF transmembrane conductance regulator (CFTR) might be responsible. I feel that there is no need to invoke other genetic contributions, and that Santis et al too readily dismiss the role of "non-genetic" factors, having examined only a few of these. Important determining factors that are difficult to measure include the adequacy of care given in early life, as well as later, and the degree of compliance with treatment regimens. Cross-infection with virulent
55
organisms within families could also be important but is not genetically determined. Such variables affect pulmonary, but not pancreatic, status. The evidence produced by Santis and colleagues, and by others,’ is consistent with the view that the &Dgr;F508 mutation is probably associated with severe disease in both the pancreas and the lungs. Our own preliminary observations suggest that other mutations affecting exon 10 should be regarded as equivalent to &Dgr;F508 (O’Rawe A, Dodge JA, unpublished). Not only do severe involvement of the lungs and the pancreas in CF tend to occur together, but also there is evidence that patients with milder pancreatic disease have lower sweat electrolyte valuessuggesting that mild and severe CF variants are not organ-specific. We should not be surprised at the fact that not all patients with a certain genetic abnormality behave in precisely the same way. Destruction of the exocrine pancreas is an end result of disordered physiology, in which duct obstruction occurs and is associated with chronic pancreatitis. The extent of pancreatic damage at particular ages will depend both on the underlying severity of the genetic disorder and on the location and number of ductules that happen to be blocked. All the genetic ingredients may be present but the rate of progress of the condition will depend on random, non-genetic factors within the organ itself. In infantile hypertonic pyloric stenosis, which also has a genetically determined predisposition, I have seen identical twins who were apparently discordant, the "unaffected" infant having radiologial evidence of pyloric hypertrophy but no vomiting. Similar cases have been recorded before. These infants shared both genes and environment. I concluded that individual physiological variables determined whether actual or only potential obstruction occurred.3 In biological systems it is not always reasonable to expect a uniform rate of progress among individuals. My point may be important because one consequence of accepting that outcomes in CF are entirely determined by gene mutations could be a fatalistic approach to management, in the belief that the genes would have the last word. The documented improvement in prognosis during the past two decades’ proves that progress can be substantially modified by non-genetic factors. Nuffield Department of Child Health, Queen’s University of Belfast, Institute of Clinical Science, Belfast BT12 6BJ, UK
J. A. DODGE
1. Gaskin K, Gurwitz D, Dune P, et al. Improved respiratory prognosis m patients with cystic fibrosis with normal fat absorption J Pediatr 1982; 100: 857-62. 2 Davis PB, Hubbard VS, di Sant’Agnese PA Low sweat electrolytes in a patient with cystic fibrosis. Am J Med 1980, 69: 643-46 3 Dodge JA. Genetics of hypertrophic pyloric stenosis. Clinics Gastroenterol 1973, 2: 523-38. 4 British Paediatric Association Working Party on Cystic Fibrosis. Cystic fibrosis in the United Kingdom 1977-85: an improving picture Br Med J 1988, 297: 1599-602.
Abnormal
neonatal
frequency of &Dgr;F508 mutation in transitory hypertrypsinaemia
SIR,—As pointed out by Dumur et al’ heterozygosity for the cystic fibrosis (CF) &Dgr;F508 mutation is more frequent than expected2 in adults with chronic bronchial hypersecretion. This suggests that heterozygotes for CF may have some mild forms of the disease. Newborn babies with CF have abnormally high levels of immunoreactive trypsin (IRT) in serum, which is the basis for a screening test.3 Using the dried blood spots collected for CF screening we looked at carrier frequencies of dF 508 mutation in babies with mildly raised IRT concentrations. In our CF screening programme 08% of newborn babies have IRT concentrations of 600 µg/l on the 4th day of life, 0-3% being above 800 µg/l (Behring units).’ In the CF population 95% of neonates have an IRT above 800 p.g/1 on day 4 and above 600 I1g/1 on day 21, 5% of CF neonates having a normal IRT (false negative). Less than 1 in 15 000 non-CF babies have the same IRT pattern as babies with CF. From January to September, 1990, 28 000 babies were screened; 149 had an IRT on day 4 of 600 µg/l and below 600
µg/l on day 21. We identified 9 &Dgr;F508 heterozygotes, who were presumed not to have CF since, for ethical reasons, they would not
be sweat-tested in the absence of persistent hypertrypsinaemia. The incidence of CF in our region is 1 in 3150 with a carrier frequency of CF of 1 in 28. In our CF population, the frequency of .’1F5o8 is slightly lower than the 70% usually reported for France,’ with an expected incidence of the .’1F 508 heterozygotes of 1 in 42. The frequency of .’1F 508 mutation reported here in a restricted population (9 in 149) is significantly higher (p < 0 01; corrected chi square) than expected. These .’1F 508 heterozygotes may have a predisposition to some mild biological abnormalities as early as the first days of life.
Supported by Association Française de Lutte contre la Mucoviscidose. We thank Dr C. Ferec (Brest) for advice. Radioisotope Service, CHRU de Caen, 14033 Caen, France
DOMINIQUE LAROCHE GEORGES TRAVERT
V, Lafitte JJ, Gervais R, et al. Abnormal distribution of cystic fibrosis &Dgr;F508 allele in adults with chronic bronchial hypersecretion. Lancet 1990, 335: 1340. Kerem BS, Rommens JM, Buchanan JA, et al. Identification of the cystic fibrosis gene: genetic analysis. Science 1989, 245: 1073-80 Crossley JR, Elliott RB, Smith PA. Dried blood spot screening for cystic fibrosis in the newborn. Lancet 1979, i: 472-74 Travert G, Duhamel JF Neonatal screening for cystic fibrosis using trypsin radioimmunoassay in blood Arch Fr Pédiatr 1983; 40: 295-98 Cystic Fibrosis Genetic Analysis Consortium. Worldwide survey of the &Dgr;F508 mutation. Am J Hum Genet 1990, 47: 354-59.
1 Dumur
2 3 4 5
&bgr;(A4)-amyloid protein and parkinsoniandementia complex of Guam SIR,—Intracellular neurofibrillary tangles are a common feature of Alzheimer’s disease (AD), older patients with Down’s syndrome, dementia pugilistica ("punch-drunk syndrome" of boxers) and the parkinsonian-dementia complex amyotrophic lateral sclerosis (PDG/ALS) that is endemic among the Chamorro people of Guam. The tangles in these disorders contain similar antigenic components,’ perhaps pointing to a common pathogenesis. The other major characteristic lesions associated with AD, the extracellular &bgr;(A4)-amyloid plaques, are thought to be absent in boxer’s dementia and PDG/ALS. However, immunohistochemistry using antibodies to the &bgr;(A4)-amyloid protein component of plaque cores has revealed "diffuse" amyloid plaques in the brains of AD, Down’s syndrome, and to some extent, normal elderly control patients3.4 which are not detectable by conventional stains. We have, to our surprise, found diffuse &bgr;(A4)-amyloid plaques in the brains of boxers with dementia pugilistica.5 We wondered whether these plaques are present in the brains of PDG/ALS patients-a question of special interest in view of the realisation that AD is probably aetiologically heterogeneous6 and that both genetic and environmental factors are implicated. We have screened paraffin-embedded, formalin-fixed sections of temporal lobe tissue from 8 patients with PDG/ALS (6 males and 2 females, aged 33-66 years) using a monoclonal antibody (4D12/2/6) raised against residues 8-17 of the &bgr;-protein. The immunocytochemical techniques are described in detail elsewhere.’ 80% formic acid was used to pretreat the sections for 20 min to increase the antigenicity of the &bgr;-protein, and sections of AD brain were used as positive controls. All the AD control brains had intense staining of the &bgr;-protein deposits throughout the cortical ribbon and to some extent within the white-matter. Little or no trace of &bgr;-protein immunoreactivity was observed in any of the PDG/ALS cases. A limited amount of &bgr;(A4)-amyloid deposition has been observed in two old (> 65 years) PDG/ALS cases;’ however, the degree of deposition was consistent with that commonly found in normal ageing.3 The cause of endemic PDG/ALS in Guam is unknown. Although clustering has been noted within families, no genetic component has yet been isolated, and epidemiological evidence strongly points to an exogenous or environmental caused One hypothesis is that the deficits in mineral metabolism result in the accumulation of calcium and aluminium deposits which may lead to neuronal degradation and neurofibrillary tangle formation.9 Another centres around the neurotoxic cycads in the Chamorro diet.8 The absence of &bgr;-amyloid immunoreactive plaques in
