749
spectrometry to the analysis of acylcarnitines in human urine, blood, and tissue. Anal Biochem 1989; 180: 331-39. 4. Rinaldo P, O’Shea JJ, Coates PM, Hale DE, Stanley CA, Tanaka K. Medium-chain
acyl-CoA dehydrogenase deficiency: diagnosis by stable-isotope dilution measurement of urinary n-hexanoylglycine and 3-phenylpropionylglycine. N Engl
J Med 1988; 319: 1308-13.
5 Roe CR, Coates PM. Acyl-CoA dehydrogenase deficiencies. In: Scriver CR, Beaudet AL, Sly WS, Valle D, eds. The metabolic basis of inherited disease, 6th ed. New York: McGraw-Hill, 1989: 889-914.
Mitochondrial function and parental effect in
sex
Huntington’s disease
SIR,-In Huntington’s disease (HD) the most specific pathological change is degeneration of the small and medium spiny neurons of the caudate nucleus and putamen. The cause of HD is unknown, although the highly penetrant autosomal dominantly inherited
genetic defect has been mapped to the short arm of chromosome 4. However, neither the gene nor a biochemical marker for the disease have been identified. The observation that late-onset cases are most
frequently associated with maternal inheritance1 whereas juvenile onset cases usually have affected fathers2,3 has raised the possibility of some maternal factor modifying age of onset. Since the sex of the affected individual is not a factor, it has been suggested that mitochondrial DNA (mtDNA) affects expression of the phenotype. All the thirteen functioning polypeptides encoded by mtDNA are part of the mitochondrial respiratory chain. Positron emission tomography has demonstrated reduced glucose metabolism in the caudate nucleus in HD,5 and this reduced hypometabolism may reflect a deficiency of the mitochondrial respiratory chain. We have examined late-onset HD brains to see if these cases are associated with altered respiratory chain enzyme activity. Post-mortem specimens of caudate nucleus, putamen, and cortex were analysed from four patients with HD and from five controls with no clinical or pathological evidence of neurological disease. Patients were matched for age (control 75 [SD 9] years, HD 67 [2] years), delay to body refrigeration (1 ’5-3 h) after death, and time to freezing of brain after death (control 21 [3], HD 24 [8] h). Brain samples were homogenised and assayed for NADH CoQl reductase (complex I), succinate cytochrome c reductase (complexes II and III), cytochrome oxidase (complex IV), and citrate synthase, and protein content was measured.6 Citrate synthase corrected enzyme activities showed a severe (77%) decrease in complexes II and III that was specific to HD caudate nucleus. Activities of complexes I and IV were within control ranges (table). These results suggest a site-specific deficiency of complexes II/III relative to mitochondrial mass in HD. Brennan et al7 found decreased succinate linked oxidation, cytochrome oxidase activity, and cytochrome aa3 levels in mitochondrial membranes isolated from HD caudate nucleus. Such preparations, however, do not allow for correction of variations in mitochondrial mass between tissues. Cytochrome oxidase activity was also decreased in our HD caudate nucleus samples, for example, but was normal when corrected for mitochondrial content. Complexes II and III comprise about fifteen polypeptides only one of which, cytochrome b, is encoded by mtDNA. Cytochrome b levels were normal in HD caudate nucleus.’ Furthermore, analysis of mtDNA in a large Venezuelan pedigree did not show any changes RESPIRATORY ENZYME ACTIVITIES CORRECTED FOR CITRATE SYNTHASE ACTIVITY
*p=0 016 (Mann-Whitney U-test)
Enzyme ac6v!t!es(nmo!/mm/mg,comp!exes!,I, II/III, K/m!n/mgcomp)ex IV [K=first order rate constant]) corrected for tissue variations citrate
synthase activity, expressed Expressed as 10’ of actual data
as mean
(SD)
m
mitochondrral content using
that could account for any maternally inherited protective factor.8 These results provide strong evidence that mtDNA and mtDNA encoded polypeptides are normal in HD. How then can the sex of the affected parent influence the age of onset in HD? One attractive theory involves genomic imprinting and suggests modification of HD expression by DNA methylation, a process strongly dependent upon parental origin.9 This effect might be mediated via regulation of a modifying gene unlinked to the HD locus on chromosome 4.8 These results contrast with respiratory chain enzyme activity in Parkinson’s disease in which there is selective deficiency of complex I activity anatomically specific for substantia nigra.6,10 It is unclear whether the complex II/III deficiency in caudate nucleus in HD is primary. However, positron emission tomography indicates hypometabolism preceding bulk tissue loss in HD. Modulation of complex II/III activity, perhaps via some developmentally regulated isoenzyme, may play some part in the determination of age of onset. Department of Neurological Science, Royal Free Hospital School of Medicine, London
V. M. MANN J. M. COOPER
Laboratory of Experimental Medicine, INSERM U289, Hôpital de la Salpêtrière, Paris, France
F. JAVOY-AGID Y. AGID
Parkinson’s Disease Society Experimental Research Laboratories,
Pharmacology Group, Biomedical Science Division,
King’s College Campus, London SW3
P.
JENNER
University Department of Clinical Neurology, Institute of Neurology, London WC1 N 3BG, UK
A. H. V. SCHAPIRA
Myers RM, Goldman D, Bird ED, et al Maternal transmission in Huntington’s disease. Lancet 1983; i: 208-10. 2. Myers RJ, Madden JJ, Teague JL, Falek A. Factors related to onset age of Huntington’s disease. Am J Med Genet 1982; 34: 481-88. 3. Hall JG, Te-Juatco L. Association between age of onset and parental inheritance in Huntington’s chorea. Am J Med Genet 1983; 16: 289-90. 4. Boehnke M, Conneally PM, Lange K. Two models for a maternal factor in the inheritance of Huntington’s disease. Am J Hum Genet 1983; 35: 845-60. 5. Kuh1 DE, Phelps ME, Markham CH, Metter EJ, Riege WH, Winter J. Cerebral metabolism and atrophy in Huntington’s disease determined by 18F-FDG and computed tomographic scan. Ann Neurol 1982; 12: 425-34. 6. Schapira AHV, Cooper JM, Dexter D, Jenner P, Clark JB, Marsden CD. Mitochondrial complex I deficiency in Parkinson’s disease. J Neurochem 1990; 54: 1.
823-27. 7. Brennan WA, Bird ED, Aprille JR Regional mitochondrial respiratory activity in 1985; 44: 1948-50. J Huntington’s disease brain. Neurochem 8. Irwin CC, Wexler NS, Young AB, et al. The role of mitochondrial DNA in Huntington’s disease. J Mol Neurosci 1989; 1: 129-36. 9. Reik W. Genomic imprinting: possible mechanism for the parental origin effect in Huntington’s chorea. J Med Genet 1988; 25: 805-08. 10. Schapira AHV, Mann VM, Cooper JM, et al. The anatomic and disease specificity of NADH CoQ reductase (complex I) deficiency in Parkinson’s disease. JNeurochem
(in press).
Heterogeneity in proximal spinal muscular atrophy SIR,-Dr Melki and colleagues (Aug 4, p 271) mapped the acute form of spinal muscular atrophy (SMA) to chromosome 5ql2-ql4. The same linkage has also been found by Gilliam and colleagues.1 Both groups have shown that chronic forms of proximal SMA are linked to the same region/,3 which suggests that different clinical forms are allelic and caused by different mutations of the same gene. In principle, these findings make possible prenatal diagnosis of SMA. We agree with the advice in the accompanying editorial (p 281) that prenatal diagnosis with DNA markers should be withheld until the question of heterogeneity is clarified. The results of our study on the genetics of proximal SMA in 234 cases from 206 families give evidence that the condition may be heterogeneous.4 In families with an affected individual in only one generation, it seems unlikely that all cases follow autosomal recessive inheritance. In a clinically defined group of patients with
750
age of onset between 6 months and 3 years who learned to walk, the
segregation ratio
compatible with autosomal recessive inheritance (0-03 ±0-05). This finding could be explained by the existence of spontaneous mutations or of non-genetic forms (phenocopies) of the disease. The latter explanation seems unlikely. Six previous studies5-10 on the genetics of proximal SMA came, with one exception6 to the conclusion that the condition is not usually inherited recessively, with a deviation predominantly in groups with later ages of onset. Hausmanowa-Petrusewicz and colleagues1o found in a group with age of onset between 10 and 36 months, similar to our study group, a significant deviation from the assumption of autosomal recessive inheritance. In linkage studies in chronic childhood SMA/,3 only families with more than one affected person or parental consanguinity were examined, thus indicating autosomal recessive inheritance. Within such families, cases that are not inherited recessively cannot be expected. We found 6 "atypical" families with at least 2 affected persons, each partly belonging to different types of SMA in different parts of the pedigrees. These pedigrees cannot be explained by autosomal recessive inheritance without additional hypotheses. Becker’s allelic model,l1 postulating a compound situation in affected persons with alleles of significantly different population frequencies, could be a suitable explanation, indicating genetic heterogeneity. There is an unexplained preponderance of males among our patients (142 males, 92 females), which is unusual in recessive conditions. Sex influence in proximal SMA is well documented. Gilliam and colleagues1 found, in both acute and chronic SMA groups,1 family possibly not linked to markers on chromosome 5q. Besides genetic heterogeneity, Gilliam et al consider the possibility of misdiagnosis in these cases, raising a serious problem in SMA. In 2 of 38 males in our study with a diagnosis of chronic SMA, a deletion in the Duchenne/Becker gene could be detected, underlining the observation that X-linked muscular dystrophy can be indistinguishable clinically from "typical" SMA.12 Thus, analysis of dystrophin is essential in patients with milder forms of SMA before DNA diagnosis. Linkage studies of many families with different clinical subgroups of SMA and only 1 affected individual can supply information on the extent of heterogeneity until the mutation(s) have been identified. Besides cases with dominant and, probably, X-linked inheritance13 of proximal SMA, there is evidence for genetic heterogeneity which could lead to false results in prenatal diagnosis. was not
The study is supported by the Deutsche Forschungsgemeinschaft and the Deutsche Gesellschaft Beckampfung der Muskelkrankhenen. Institute for Human Genetics of Bonn University, D-5300 Bonn 1, West Germany
KLAUS ZERRES SABINE RUDNIK-SCHÖNEBORN MARCELLA RIETSCHEL
1. Gilliam TC, Brzustovic LM, Castilla LH, et al. Genetic homogeneity between acute and chronic forms of spinal muscular atrophy. Nature 1990; 345: 823-25. 2. Brzustowicz LM, Lehner T, Castilla LH, et al. Genetic mapping of chronic childhood-onset spinal muscular atrophy to chromosome 5q11 2-13 3. Nature 1990; 344: 540-41. 3. Melki J, Abdelhak S, Sheth P, et al. Gene for chronic proximal spinal muscular atrophies maps to chromosome 5q. Nature 1990; 344: 767-68. 4. Zerres K Klassifikation and genetik spinaler muskelatrophien. Stuttgart: Georg Thieme, 1989. 5. Brandt S. Werdnig-Hoffmann’s infantile progressive muscular atrophy. Copenhagen: Ejnar Munksgaard, 1951. 6. Winsor EJ, Murphy EG, Thompson MW, et al. Genetics of childhood spinal muscular atrophy. J Med Genet 1971; 8: 143-48. 7. Bundey S, Lovelace RE A clinical and genetic study of chronic proximal spinal muscular atropy. Brain 1975; 98: 455-72. 8. Emery AEH, Davie AM, Holloway S, et al. International collaborative study of the spinal muscular atrophies, part II: analysis of genetic data J Neurol Sci 1976; 30: 375-84. 9. Pearn J. Segregation analysis of chronic childhood spinal muscular atrophy. J Med
Genet 1978; 15: 418-23. 10. Hausmanowa-Petrusewicz I, Zaremba J, Borkowska J, et al. Chronic proximal spinal muscular atrophy of childhood and adolescence: problems of classification and genetic counselling. J Med Genet 1985; 22: 350-53. 11. Zerres K, Stephen M, Kehren U, et al. Becker’s allelic model to explain unusual pedigrees with spinal muscular atrophy. Clin Genet 1987; 31: 276-77. 12 Lunt PW, Cumming WJK, Kingston H, et al. DNA probes in differential diagnosis of Becker muscular dystrophy and spinal muscular atrophy Lancet 1989; i: 46-47.
13.
Greenberg F, Fenolio KR, Hejtmancik JF, et al. atrophy. Am J Dis Child 1988; 142: 217-19.
X-linked infantile
spinal muscular
Post-kala-azar dermal leishmaniasis in the absence of active visceral leishmaniasis SiR,—In a field survey for visceral leishmaniasis, 11 cases (8 male, 3 female) of post-kala-azar dermal leishmaniasis (PKDL) were found in a cluster of hamlets and villages near the Sudan-Ethiopia border with a population of about 5000. The area is an endemic focus for visceral leishmaniasis. 8 patients were children aged between 2 and 12 years. PKDL had developed in 10 patients 4-6 months after treatment for visceral leishmaniasis; however, 1 adult gave no previous history of visceral leishmaniasis.1 patient was diagnosed as having lepromatous leprosy on clinical grounds, and had been on antileprosy treatment for 5 years without benefit. Another case was mistaken for tuberculoid leprosy on skin biopsy. No cases of active leishmaniasis were found in the villages at the time of the survey (March, 1990). Parasites were detected in slit smears and/or skin biopsy specimens of all patients. A direct agglutination test (DAT) for antibodies to leishmania parasites was positive in all patients, but was negative in their parents and in 10 controls with leprosy. In one child PKDL regressed spontaneously. The others were treated with pentostam and are being followed up. We wish to draw attention to the importance of recognising PKDL, its potential role in the transmission of infection in endemic areas, and to the fact that it may occur in the absence of active visceral leishmaniasis. The demonstration of amastigotes in the lesion and a positive DAT help to confirm the diagnosis of PKDL and to exclude leprosy in doubtful cases. The persistence of the disease (10 years in 1 patient) makes transmission from those infected via a phelobotomine vector highly probable and may determine the epidemiological characteristics of kala-azar in some foci. The villages will be monitored for the appearance of active cases of visceral leishmaniasis.
Leishmaniasis Research Group, Faculty of Medicine, University of Khartoum, PO Box 102, Khartoum, Sudan, and Institute of Tropical Medicine, Khartoum
A. M. EL-HASSAN H. W. GHALIB E. ZYLSTRA I. A. ELTOUM M. S. ALI H. M. A. AHMED
Non-specificity of anti-HCV test for seroepidemiological analysis SiR,—Preliminary data from industrialised countries have revealed prevalence of hepatitis C virus (HCV) antibody of less than 3% in the general population. In developing countries the frequency is higher. Using the Chiron/Ortho ELISA to evaluate the prevalence of anti-HCV in an isolated Pacific island population, we have come up with some unexpected results.
a
We studied sera from members of the Kwaio tribe on Malaita in the Solomon Islands. Disease patterns are typical for a tropical, developing society-acute infections, accidents, and malaria being the main causes of illness and death.l The sera had been collected in 1966, from presumably healthy volunteers, as part of an ecological study. They had been stored at - 20 or - 70°C and had not been heated. Equal numbers (183) of males and females of all ages from 2 to 72 years were represented in the panel. 18 representative sera were tested for hepatitis A antibody, hepatitis B surface antigen and antibody, and hepatitis B core antibody by commercial radioimmunoassays (Abbott Laboratories). All sera positive for HBsAg were tested for delta antigen by a non-commercial RIN and for delta antibody by an Abbott Laboratories RIA. Sera that were positive for anti-HCV by ELISA (Ortho Diagnostic Systems) were retested at Abbott Laboratories with tests based on recombinant proteins or synthetic peptides. One confirmatory test was based on synthetic purified peptide segments of C-100 coated on polystyrene beads and used in an ELI SA format. The second confirmatory test made use of neutralisation reagent consisting of most of the aminoacid sequences of C-100, expressed in Escherichia coli rather than yeast: the principle is that HCV antigen in solution may inhibit antibody from binding to C-100 antigen coated polystyrene beads, and 50% or greater inhibition by the addition of neutralisation
spectrometry to the analysis of acylcarnitines in human urine, blood, and tissue. Anal Biochem 1989; 180: 331-39. 4. Rinaldo P, O’Shea JJ, Coates PM, Hale DE, Stanley CA, Tanaka K. Medium-chain
acyl-CoA dehydrogenase deficiency: diagnosis by stable-isotope dilution measurement of urinary n-hexanoylglycine and 3-phenylpropionylglycine. N Engl
J Med 1988; 319: 1308-13.
5 Roe CR, Coates PM. Acyl-CoA dehydrogenase deficiencies. In: Scriver CR, Beaudet AL, Sly WS, Valle D, eds. The metabolic basis of inherited disease, 6th ed. New York: McGraw-Hill, 1989: 889-914.
Mitochondrial function and parental effect in
sex
Huntington’s disease
SIR,-In Huntington’s disease (HD) the most specific pathological change is degeneration of the small and medium spiny neurons of the caudate nucleus and putamen. The cause of HD is unknown, although the highly penetrant autosomal dominantly inherited
genetic defect has been mapped to the short arm of chromosome 4. However, neither the gene nor a biochemical marker for the disease have been identified. The observation that late-onset cases are most
frequently associated with maternal inheritance1 whereas juvenile onset cases usually have affected fathers2,3 has raised the possibility of some maternal factor modifying age of onset. Since the sex of the affected individual is not a factor, it has been suggested that mitochondrial DNA (mtDNA) affects expression of the phenotype. All the thirteen functioning polypeptides encoded by mtDNA are part of the mitochondrial respiratory chain. Positron emission tomography has demonstrated reduced glucose metabolism in the caudate nucleus in HD,5 and this reduced hypometabolism may reflect a deficiency of the mitochondrial respiratory chain. We have examined late-onset HD brains to see if these cases are associated with altered respiratory chain enzyme activity. Post-mortem specimens of caudate nucleus, putamen, and cortex were analysed from four patients with HD and from five controls with no clinical or pathological evidence of neurological disease. Patients were matched for age (control 75 [SD 9] years, HD 67 [2] years), delay to body refrigeration (1 ’5-3 h) after death, and time to freezing of brain after death (control 21 [3], HD 24 [8] h). Brain samples were homogenised and assayed for NADH CoQl reductase (complex I), succinate cytochrome c reductase (complexes II and III), cytochrome oxidase (complex IV), and citrate synthase, and protein content was measured.6 Citrate synthase corrected enzyme activities showed a severe (77%) decrease in complexes II and III that was specific to HD caudate nucleus. Activities of complexes I and IV were within control ranges (table). These results suggest a site-specific deficiency of complexes II/III relative to mitochondrial mass in HD. Brennan et al7 found decreased succinate linked oxidation, cytochrome oxidase activity, and cytochrome aa3 levels in mitochondrial membranes isolated from HD caudate nucleus. Such preparations, however, do not allow for correction of variations in mitochondrial mass between tissues. Cytochrome oxidase activity was also decreased in our HD caudate nucleus samples, for example, but was normal when corrected for mitochondrial content. Complexes II and III comprise about fifteen polypeptides only one of which, cytochrome b, is encoded by mtDNA. Cytochrome b levels were normal in HD caudate nucleus.’ Furthermore, analysis of mtDNA in a large Venezuelan pedigree did not show any changes RESPIRATORY ENZYME ACTIVITIES CORRECTED FOR CITRATE SYNTHASE ACTIVITY
*p=0 016 (Mann-Whitney U-test)
Enzyme ac6v!t!es(nmo!/mm/mg,comp!exes!,I, II/III, K/m!n/mgcomp)ex IV [K=first order rate constant]) corrected for tissue variations citrate
synthase activity, expressed Expressed as 10’ of actual data
as mean
(SD)
m
mitochondrral content using
that could account for any maternally inherited protective factor.8 These results provide strong evidence that mtDNA and mtDNA encoded polypeptides are normal in HD. How then can the sex of the affected parent influence the age of onset in HD? One attractive theory involves genomic imprinting and suggests modification of HD expression by DNA methylation, a process strongly dependent upon parental origin.9 This effect might be mediated via regulation of a modifying gene unlinked to the HD locus on chromosome 4.8 These results contrast with respiratory chain enzyme activity in Parkinson’s disease in which there is selective deficiency of complex I activity anatomically specific for substantia nigra.6,10 It is unclear whether the complex II/III deficiency in caudate nucleus in HD is primary. However, positron emission tomography indicates hypometabolism preceding bulk tissue loss in HD. Modulation of complex II/III activity, perhaps via some developmentally regulated isoenzyme, may play some part in the determination of age of onset. Department of Neurological Science, Royal Free Hospital School of Medicine, London
V. M. MANN J. M. COOPER
Laboratory of Experimental Medicine, INSERM U289, Hôpital de la Salpêtrière, Paris, France
F. JAVOY-AGID Y. AGID
Parkinson’s Disease Society Experimental Research Laboratories,
Pharmacology Group, Biomedical Science Division,
King’s College Campus, London SW3
P.
JENNER
University Department of Clinical Neurology, Institute of Neurology, London WC1 N 3BG, UK
A. H. V. SCHAPIRA
Myers RM, Goldman D, Bird ED, et al Maternal transmission in Huntington’s disease. Lancet 1983; i: 208-10. 2. Myers RJ, Madden JJ, Teague JL, Falek A. Factors related to onset age of Huntington’s disease. Am J Med Genet 1982; 34: 481-88. 3. Hall JG, Te-Juatco L. Association between age of onset and parental inheritance in Huntington’s chorea. Am J Med Genet 1983; 16: 289-90. 4. Boehnke M, Conneally PM, Lange K. Two models for a maternal factor in the inheritance of Huntington’s disease. Am J Hum Genet 1983; 35: 845-60. 5. Kuh1 DE, Phelps ME, Markham CH, Metter EJ, Riege WH, Winter J. Cerebral metabolism and atrophy in Huntington’s disease determined by 18F-FDG and computed tomographic scan. Ann Neurol 1982; 12: 425-34. 6. Schapira AHV, Cooper JM, Dexter D, Jenner P, Clark JB, Marsden CD. Mitochondrial complex I deficiency in Parkinson’s disease. J Neurochem 1990; 54: 1.
823-27. 7. Brennan WA, Bird ED, Aprille JR Regional mitochondrial respiratory activity in 1985; 44: 1948-50. J Huntington’s disease brain. Neurochem 8. Irwin CC, Wexler NS, Young AB, et al. The role of mitochondrial DNA in Huntington’s disease. J Mol Neurosci 1989; 1: 129-36. 9. Reik W. Genomic imprinting: possible mechanism for the parental origin effect in Huntington’s chorea. J Med Genet 1988; 25: 805-08. 10. Schapira AHV, Mann VM, Cooper JM, et al. The anatomic and disease specificity of NADH CoQ reductase (complex I) deficiency in Parkinson’s disease. JNeurochem
(in press).
Heterogeneity in proximal spinal muscular atrophy SIR,-Dr Melki and colleagues (Aug 4, p 271) mapped the acute form of spinal muscular atrophy (SMA) to chromosome 5ql2-ql4. The same linkage has also been found by Gilliam and colleagues.1 Both groups have shown that chronic forms of proximal SMA are linked to the same region/,3 which suggests that different clinical forms are allelic and caused by different mutations of the same gene. In principle, these findings make possible prenatal diagnosis of SMA. We agree with the advice in the accompanying editorial (p 281) that prenatal diagnosis with DNA markers should be withheld until the question of heterogeneity is clarified. The results of our study on the genetics of proximal SMA in 234 cases from 206 families give evidence that the condition may be heterogeneous.4 In families with an affected individual in only one generation, it seems unlikely that all cases follow autosomal recessive inheritance. In a clinically defined group of patients with
750
age of onset between 6 months and 3 years who learned to walk, the
segregation ratio
compatible with autosomal recessive inheritance (0-03 ±0-05). This finding could be explained by the existence of spontaneous mutations or of non-genetic forms (phenocopies) of the disease. The latter explanation seems unlikely. Six previous studies5-10 on the genetics of proximal SMA came, with one exception6 to the conclusion that the condition is not usually inherited recessively, with a deviation predominantly in groups with later ages of onset. Hausmanowa-Petrusewicz and colleagues1o found in a group with age of onset between 10 and 36 months, similar to our study group, a significant deviation from the assumption of autosomal recessive inheritance. In linkage studies in chronic childhood SMA/,3 only families with more than one affected person or parental consanguinity were examined, thus indicating autosomal recessive inheritance. Within such families, cases that are not inherited recessively cannot be expected. We found 6 "atypical" families with at least 2 affected persons, each partly belonging to different types of SMA in different parts of the pedigrees. These pedigrees cannot be explained by autosomal recessive inheritance without additional hypotheses. Becker’s allelic model,l1 postulating a compound situation in affected persons with alleles of significantly different population frequencies, could be a suitable explanation, indicating genetic heterogeneity. There is an unexplained preponderance of males among our patients (142 males, 92 females), which is unusual in recessive conditions. Sex influence in proximal SMA is well documented. Gilliam and colleagues1 found, in both acute and chronic SMA groups,1 family possibly not linked to markers on chromosome 5q. Besides genetic heterogeneity, Gilliam et al consider the possibility of misdiagnosis in these cases, raising a serious problem in SMA. In 2 of 38 males in our study with a diagnosis of chronic SMA, a deletion in the Duchenne/Becker gene could be detected, underlining the observation that X-linked muscular dystrophy can be indistinguishable clinically from "typical" SMA.12 Thus, analysis of dystrophin is essential in patients with milder forms of SMA before DNA diagnosis. Linkage studies of many families with different clinical subgroups of SMA and only 1 affected individual can supply information on the extent of heterogeneity until the mutation(s) have been identified. Besides cases with dominant and, probably, X-linked inheritance13 of proximal SMA, there is evidence for genetic heterogeneity which could lead to false results in prenatal diagnosis. was not
The study is supported by the Deutsche Forschungsgemeinschaft and the Deutsche Gesellschaft Beckampfung der Muskelkrankhenen. Institute for Human Genetics of Bonn University, D-5300 Bonn 1, West Germany
KLAUS ZERRES SABINE RUDNIK-SCHÖNEBORN MARCELLA RIETSCHEL
1. Gilliam TC, Brzustovic LM, Castilla LH, et al. Genetic homogeneity between acute and chronic forms of spinal muscular atrophy. Nature 1990; 345: 823-25. 2. Brzustowicz LM, Lehner T, Castilla LH, et al. Genetic mapping of chronic childhood-onset spinal muscular atrophy to chromosome 5q11 2-13 3. Nature 1990; 344: 540-41. 3. Melki J, Abdelhak S, Sheth P, et al. Gene for chronic proximal spinal muscular atrophies maps to chromosome 5q. Nature 1990; 344: 767-68. 4. Zerres K Klassifikation and genetik spinaler muskelatrophien. Stuttgart: Georg Thieme, 1989. 5. Brandt S. Werdnig-Hoffmann’s infantile progressive muscular atrophy. Copenhagen: Ejnar Munksgaard, 1951. 6. Winsor EJ, Murphy EG, Thompson MW, et al. Genetics of childhood spinal muscular atrophy. J Med Genet 1971; 8: 143-48. 7. Bundey S, Lovelace RE A clinical and genetic study of chronic proximal spinal muscular atropy. Brain 1975; 98: 455-72. 8. Emery AEH, Davie AM, Holloway S, et al. International collaborative study of the spinal muscular atrophies, part II: analysis of genetic data J Neurol Sci 1976; 30: 375-84. 9. Pearn J. Segregation analysis of chronic childhood spinal muscular atrophy. J Med
Genet 1978; 15: 418-23. 10. Hausmanowa-Petrusewicz I, Zaremba J, Borkowska J, et al. Chronic proximal spinal muscular atrophy of childhood and adolescence: problems of classification and genetic counselling. J Med Genet 1985; 22: 350-53. 11. Zerres K, Stephen M, Kehren U, et al. Becker’s allelic model to explain unusual pedigrees with spinal muscular atrophy. Clin Genet 1987; 31: 276-77. 12 Lunt PW, Cumming WJK, Kingston H, et al. DNA probes in differential diagnosis of Becker muscular dystrophy and spinal muscular atrophy Lancet 1989; i: 46-47.
13.
Greenberg F, Fenolio KR, Hejtmancik JF, et al. atrophy. Am J Dis Child 1988; 142: 217-19.
X-linked infantile
spinal muscular
Post-kala-azar dermal leishmaniasis in the absence of active visceral leishmaniasis SiR,—In a field survey for visceral leishmaniasis, 11 cases (8 male, 3 female) of post-kala-azar dermal leishmaniasis (PKDL) were found in a cluster of hamlets and villages near the Sudan-Ethiopia border with a population of about 5000. The area is an endemic focus for visceral leishmaniasis. 8 patients were children aged between 2 and 12 years. PKDL had developed in 10 patients 4-6 months after treatment for visceral leishmaniasis; however, 1 adult gave no previous history of visceral leishmaniasis.1 patient was diagnosed as having lepromatous leprosy on clinical grounds, and had been on antileprosy treatment for 5 years without benefit. Another case was mistaken for tuberculoid leprosy on skin biopsy. No cases of active leishmaniasis were found in the villages at the time of the survey (March, 1990). Parasites were detected in slit smears and/or skin biopsy specimens of all patients. A direct agglutination test (DAT) for antibodies to leishmania parasites was positive in all patients, but was negative in their parents and in 10 controls with leprosy. In one child PKDL regressed spontaneously. The others were treated with pentostam and are being followed up. We wish to draw attention to the importance of recognising PKDL, its potential role in the transmission of infection in endemic areas, and to the fact that it may occur in the absence of active visceral leishmaniasis. The demonstration of amastigotes in the lesion and a positive DAT help to confirm the diagnosis of PKDL and to exclude leprosy in doubtful cases. The persistence of the disease (10 years in 1 patient) makes transmission from those infected via a phelobotomine vector highly probable and may determine the epidemiological characteristics of kala-azar in some foci. The villages will be monitored for the appearance of active cases of visceral leishmaniasis.
Leishmaniasis Research Group, Faculty of Medicine, University of Khartoum, PO Box 102, Khartoum, Sudan, and Institute of Tropical Medicine, Khartoum
A. M. EL-HASSAN H. W. GHALIB E. ZYLSTRA I. A. ELTOUM M. S. ALI H. M. A. AHMED
Non-specificity of anti-HCV test for seroepidemiological analysis SiR,—Preliminary data from industrialised countries have revealed prevalence of hepatitis C virus (HCV) antibody of less than 3% in the general population. In developing countries the frequency is higher. Using the Chiron/Ortho ELISA to evaluate the prevalence of anti-HCV in an isolated Pacific island population, we have come up with some unexpected results.
a
We studied sera from members of the Kwaio tribe on Malaita in the Solomon Islands. Disease patterns are typical for a tropical, developing society-acute infections, accidents, and malaria being the main causes of illness and death.l The sera had been collected in 1966, from presumably healthy volunteers, as part of an ecological study. They had been stored at - 20 or - 70°C and had not been heated. Equal numbers (183) of males and females of all ages from 2 to 72 years were represented in the panel. 18 representative sera were tested for hepatitis A antibody, hepatitis B surface antigen and antibody, and hepatitis B core antibody by commercial radioimmunoassays (Abbott Laboratories). All sera positive for HBsAg were tested for delta antigen by a non-commercial RIN and for delta antibody by an Abbott Laboratories RIA. Sera that were positive for anti-HCV by ELISA (Ortho Diagnostic Systems) were retested at Abbott Laboratories with tests based on recombinant proteins or synthetic peptides. One confirmatory test was based on synthetic purified peptide segments of C-100 coated on polystyrene beads and used in an ELI SA format. The second confirmatory test made use of neutralisation reagent consisting of most of the aminoacid sequences of C-100, expressed in Escherichia coli rather than yeast: the principle is that HCV antigen in solution may inhibit antibody from binding to C-100 antigen coated polystyrene beads, and 50% or greater inhibition by the addition of neutralisation
