Hereditary distal spinal muscular atrophy. A report on 34 cases and a review of the literature

Mapping of autosomal recessive chronic distal spinal muscular atrophy to chromosome 11q13

Distal spinal muscular atrophy is a heterogeneous group of neuromuscular disorders caused by progressive anterior horn cell degeneration and characterized by progressive motor weakness and muscular atrophy, predominantly in the distal parts of the limbs. Here we report on chronic autosomal recessive distal spinal muscular atrophy in a large, inbred family with onset at various ages. Because this condition had some of the same clinical features as spinal muscular atrophy with respiratory distress, we tested the disease gene for linkage to chromosome 11q and mapped the disease locus to chromosome 11q13 in the genetic interval that included the spinal muscular atrophy with respiratory distress gene (D11S1889-D11S1321, Z(max) = 4.59 at theta = 0 at locus D11S4136). The sequencing of IGHMBP2, the human homologue of the mouse neuromuscular degeneration gene (nmd) that accounts for spinal muscular atrophy with respiratory distress, failed to detect any mutation in our chronic distal spinal muscular atrophy patients, suggesting that spinal muscular atrophy with respiratory distress and chronic distal spinal muscular atrophy are caused by distinct genes located in the same chromosomal region. In addition, the high intrafamilial variability in age at onset raises the question of whether nonallelic modifying genes could be involved in chronic distal spinal muscular atrophy.

Autosomal dominant distal spinal muscular atrophy: an Italian family not linked to 12q24 and 7p14

Distal spinal muscular atrophy is genetically heterogeneous, as sporadic cases and both autosomal dominant and recessive inheritance have been described. An autosomal dominant distal spinal muscular atrophy with upper limb predominance has been mapped to chromosome 7p, and more recently, an autosomal dominant distal spinal muscular atrophy with lower limb predominance has been linked to chromosome 12q24. We describe a four generation Italian family with autosomal dominant distal spinal muscular atrophy starting between 8 and 30 years with weakness and atrophy of distal leg muscles. The older patients also presented sensorineural deafness. We performed genetic linkage analysis with microsatellite markers D12S366, D12S349, D12S86, D12S321, D12S1612, D12S1349, D12S342, PLA2A on chromosome 12q24 and D7S516, D7S2496, D7S632, D7S2252 on chromosome 7p14. No support for linkage to chromosome 12q24 and 7p14 was found in our family, confirming a genetic heterogeneity within autosomal dominant distal spinal muscular atrophy.

Progress in clinical neurosciences: Charcot-Marie-Tooth disease and related inherited peripheral neuropathies

The classification of Charcot-Marie-Tooth disease and related hereditary motor and sensory neuropathies has evolved to incorporate clinical, electrophysiological and burgeoning molecular genetic information that characterize the many disorders. For several inherited neuropathies, the gene product abnormality is known and for others, candidate genes have been identified. Genetic testing can pinpoint a specific inherited neuropathy for many patients. However, clinical and electrophysiological assessments continue to be essential tools for diagnosis and management of this disease group. This article reviews clinical, electrophysiological, pathological and molecular aspects of hereditary motor and sensory neuropathies.

SMN2-deletion in childhood-onset spinal muscular atrophy

The human genome has two homologous survival motor neuron genes, SMN1 and SMN2. Although deletions of SMN1 are frequently reported in childhood-onset spinal muscular atrophy (SMA), SMN2 have been found to be intact in patients with the disorder. We report on a 5-year-old boy with childhood-onset SMA who has a homozygous deletion of SMN2. He had wasting, weakness, and hyporeflexia, predominantly in the distal muscles. The muscles involved showed chronic neurogenic changes on electromyogram. There was no sensory involvement. A nerve conduction study showed near normal conduction velocity with reduction in the amplitude of the compound muscle action potential. Analysis of polymerase chain reaction-restriction fragment length polymorphism as well as single-strand conformation polymorphism on exons 7 and 8 of the SMN genes revealed the SMN2-deletion. Base sequencing and densitometric analysis of the critical region (exon 7) did not show any microdeletion or duplication of SMN1, but confirmed the deletion of SMN2. We conclude that a deletion of SMN2 may also result in the SMA phenotype.

Localization of the gene for distal hereditary motor neuronopathy VII (dHMN-VII) to chromosome 2q14

Distal hereditary motor neuronopathy type VII (dHMN-VII) is an autosomal dominant disorder characterized by distal muscular atrophy and vocal cord paralysis. We performed a genomewide linkage search in a large Welsh pedigree with dHMN-VII and established linkage to chromosome 2q14. Analyses of a second family with dHMN-VII confirmed the location of the gene and provided evidence for a founder mutation segregating in both pedigrees. The maximum three-point LOD score in the combined pedigree was 7.49 at D2S274. Expansion of a polyalanine tract in Engrailed-1, a transcription factor strongly expressed in the spinal cord, was excluded as the cause of dHMN-VII.

Charcot-Marie-Tooth disease (CMT): distinctive phenotypic and genotypic features in CMT type 2

Charcot-Marie-Tooth disease (CMT), or hereditary motor and sensory neuropathy (HMSN), includes two main subtypes of CMT1/HMSN I (demyelinating), and CMT2/HMSN II (axonal). Further heterogeneity has been demonstrated by genetic molecular studies, with at least four responsible genes for CMT1. As for CMT2, a mutation in the neurofilament-light (NF-L) gene has been identified in a single family, and other CMT2 loci have been mapped. We propose a clinical classification of the CMT2 phenotypes, and review the features of the identified CMT2 genotypes. The following main subtypes of CMT2 are considered in the phenotype classification: classical CMT2, the variants of CMT2 showing atypical features that may represent either variance in the classical CMT2 phenotype or separate entities; CMT2 plus, i.e. complex forms with involvement of additional neural structures. The recognized CMT2 genotypes include: CMT2A (mapped to chromosome 1p35-36); CMT2B (3q13-22); CMT2C (with vocal cord paresis); CMT2D (7p14); CMT2E, related to a mutation in the NF-L gene on chromosome 8p21; proximal CMT2, or HMSN P (3q13.1); CMT2 with MPZ mutations; autosomal recessive CMT2 (1q21.2-q21.3); agenesis of the corpus callosum with sensorimotor neuronopathy (15q13-q15); CMT2 X-linked with deafness and mental retardation (Xq24-q26). The identified genotypes may correspond to previously described clinical subtypes of CMT2. In particular, classical CMT2 presents in association with NF-L gene mutation, in the only CMT2 family with known gene mutation, and in CMT2A patients. However, the features of classical CMT2 have been paradoxically reported also in families with MPZ mutation, and conversely several CMT2 families are not linked to the known CMT2 loci. Further cloning of the CMT2 genes will ultimately shed light on the pathogenic mechanism(s) implicated in the process of axonal degeneration, shared by the different CMT2 genotypes.

A clone contig of 12q24.3 encompassing the distal hereditary motor neuropathy type II gene

We previously assigned the disease locus for autosomal dominant hereditary motor neuropathy type II (distal HMN II) within a 13-cM interval at chromosome 12q24.3. We constructed a physical map of the distal HMN II region based on yeast artificial chromosomes (YACs), P1 artificial chromosomes (PACs), and bacterial artificial chromosomes (BACs) using an STS content mapping approach. The contig contains 26 YAC, 15 PAC, and 60 BAC clones and covers a physical distance of approximately 5 Mb. A total of 99 STS markers, including 25 known STSs and STRs, 49 new STSs generated from clone end-fragments, 20 ESTs, and 5 known genes, were located on the contig. This physical map provides a valuable resource for mapping genes and markers located within the distal HMN II region and facilitates the positional cloning of the distal HMN II gene.

Autosomal dominant distal spinal muscular atrophy type V (dSMA-V) and Charcot-Marie-Tooth disease type 2D (CMT2D) segregate within a single large kindred and map to a refined region on chromosome 7p15

Two separate disorders, autosomal dominant distal spinal muscular atrophy type V (dSMA-V) characterized by marked bilateral weakness in the hands and atrophy of thenar eminence and the first interosseous muscle, and Charcot-Marie-Tooth disease type 2D (CMT2D) characterized by sensory deficits in addition to the upper limb weakness and wasting, have been independently linked to chromosome 7p. We identified a multigenerational Mongolian kindred with 17 members affected with either dSMA-V or CMT2D and mapped both syndromes to the same region on chromosome 7p15. A maximum two-point lod score of 4.74 at recombination fraction zero was obtained with marker D7S474. Tight linkage without recombination was also detected with markers D7S526 and D7S632. A multipoint lod score of 6.07 suggested that the gene is located between markers D7S526 and D7S474. A single conserved haplotype was associated with dSMA-V and CMT2D. Based on informative recombination events, the disease locus was placed between markers D7S516 and D7S1514 within the 7p15 band. Data obtained from this study suggest that a single gene is responsible for both syndromes, dSMA-V and CMT2D, and extend our knowledge of the candidate region.

Congenital autosomal dominant distal spinal muscular atrophy

We present a father and son with congenital foot deformity. The father at age 41 years used crutches and the son at 7 years walked unaided. Both had atrophy and weakness of lower leg muscles and mild proximal and hand intrinsic weakness. Knee and ankle myotactic reflexes were absent and sensation was intact. Creatine kinase level was normal, nerve conduction studies wer normal and electromyography showed chronic neurogenic change. In both, nerve biopsies were normal and muscle biopsies showed type 1 predominance. The boy's serum hexosaminidase, spinal MRI and SMN gene were normal. This may be the first well documented example of congenital autosomal dominant distal spinal muscular atrophy affecting legs and arms.

Distal hereditary upper limb muscular atrophy

OBJECTIVES

To identify the clinical, electrophysiological, and genetic characteristics of a family with an unusual form of hereditary motor neuron disease.

METHODS

Surviving members of a pedigree in which affected members presented with weakness and atrophy of distal musculature in the upper limbs were examined clinically and electrophysiologically, and had genetic testing.

RESULTS

The disease was autosomal dominantly inherited and manifested as weakness and atrophy of distal musculature in the upper limbs, with minimal involvement of lower limbs, brisk reflexes, minimal sensory findings, and considerable variability in severity among the affected persons. Nerve conduction studies disclosed near normal motor conduction velocity, reduced motor compound action potential amplitude, prolonged distal motor latency, prolonged sensory latency, and normal sensory compound action potential amplitude. Needle electrode examination showed reduced number and increased size of motor unit potentials, but no fibrillations or fasciculations.

CONCLUSION

Distal upper limb muscular atrophy is a distinct clinical entity.

SMN gene analysis of the spinal form of Charcot-Marie-Tooth disease

The spinal form of Charcot-Marie-Tooth disease (spinal CMT) is a rare genetic disorder of the peripheral nervous system, the genetic basis of which remains unknown. To test the hypothesis that a defect of survival motor neuron (SMN), the determining gene for spinal muscular atrophy (SMA), would result in spinal CMT, 18 unrelated spinal CMT patients were studied. Nine of them were sporadic cases and the other nine belonged to unrelated autosomal dominant pedigrees. None of the 18 patients showed deletions involving SMN exons 7 or 8, the most frequent gene alteration found in SMA. In addition, haplotype analysis in two large autosomal dominant pedigrees showed that the 5q13 locus was not segregating with the spinal CMT locus. Therefore, neither the sporadic nor the familial cases of spinal CMT are associated with a SMN gene deletion, nor are the familial cases linked to the 5q13 region, indicating that this neuropathy is genetically different from SMA.

The pathology of charcot-marie-tooth disease and related disorders

Approximately a quarter of a century ago, the disorders originally designated as Charcot-Marie-Tooth disease and Dejerine-Sottas disease were shown by combined clinical, electrophysiological and nerve biopsy studies to be genetically complex. In pathological terms they could be broadly classified into demyelinating neuropathies and axonopathies. Advances in the molecular genetics of these disorders, particularly for those with a demyelinating basis, have recently produced substantial new insights. The identification of mutations in genes for myelin proteins has provided the opportunity for investigating the precise mechanisms of these neuropathies, including the use of spontaneous and genetically engineered animal models.

[Charcot-Marie-Tooth disease. Electromyographic studies in 45 patients]

The electrophysiological studies of 45 patients with Charcot-Marie-Tooth disease (CMT) are presented. The nerve conduction of the motor median and ulnar nerves permitted us to separate our patients in two types: type I (demyelinating) with motor nerve conduction (MNC) below 38 m/s (11 cases) and type II with MNC normal or above 38 m/s (34 cases). In type I there was no correlation between reduction in MNC and clinical severity. It was not possible to classify the disease on the sural nerve sensory action potential (SAP). They were unobtainable in most cases. In many patients with CMT type II the MNC was normal. In the cases the sural SAP was absent or reduced. We concluded that the MNC study is the best useful test to classify CMT disease in type I and type II.

Dominant congenital benign spinal muscular atrophy

The affected members of the family described in this article exhibit congenital nonprogressive atrophy and weakness of lower limb muscles in association with contractures. Clinical and laboratory findings support a dominant lower motor neuron disorder. DNA analysis excluded linkage of the disease with SMA markers on the long arm of chromosome 5. The condition must be differentiated from congenital and infantile SMA, from "arthrogryposis multiplex congenita, distal type," and from non hereditary types of congenital arthrogryposis.

[Infantile spinal amyotrophy with atypical course: report of 2 cases]

The authors report two cases of infantile spinal muscular atrophy with atypical evolution diagnosed by means of EMG findings. The first one is a 10 years-old female child who has showed a distal predominium of the muscle weakness and atrophy. The second patient, a 7 year-old female child, has manifested within a period of 4 months a rapidly progressive tetraparesis that culminated in death after 10 months. The authors present the most accepted classifications of the illness and discuss the clinical manifestations of the two patients aiming to characterize the clinical forms, in accordance to the literature.

Dominant inherited distal spinal muscular atrophy with atrophic and hypertrophic calves

The clinical, electrophysiological, radiological and morphological data of 3 members of a family with autosomal dominant distal spinal muscular atrophy (DSMA) are reported. One patient has the clinical picture of peroneal muscular atrophy with atrophic calves. His father and sister suffer from cramps and fasciculations of the calves with true neurogenic muscular hypertrophy of the calves. The electromyogram and the biopsy specimen are conclusive for motor neuron disease in this family. These findings suggest that the DSMA variant as described by D'Alessandro et al. (Arch. Neurol. (1982) 39: 657-660), concerning benign spinal muscular atrophy with hypertrophy of the calves, has to be considered as a mild manifestation of DSMA.

Werdnig-Hoffmann disease and chronic distal spinal muscular atrophy with apparent autosomal dominant inheritance

We report on a family in which both Werdnig-Hoffmann disease (severe infantile-onset spinal muscular atrophy) and chronic distal spinal muscular atrophy occurred, with apparent autosomal dominant inheritance. The female proband clinically had Werdnig-Hoffmann disease and died at 10 months. In their second decade of life, the proband's father and his 2 brothers developed bilateral progressive atrophy and weakness of the hands and mild weakness in the distal parts of the legs. Their mother had no symptoms or signs of motor neuron disease but electromyography revealed distal denervation of the limbs. While the family studies suggest autosomal dominant inheritance, it is possible that the proband's condition was influenced by a maternally derived allelic or modifying trait.

Benign monomelic amyotrophy of lower limb: report of three cases

Three patients with wasting confined to a single lower limb are reported. The characteristic features were: sporadic occurrence, insidious onset with slow progression and in 2 cases arrested course for at least 4 years, wasting out of proportion with disability, absence of sensory, pyramidal tract or bulbar signs. CK, motor and sensory conductions, and lumbar MRI were normal. Muscle CT showed selective loss of muscle tissue and fat replacement in posterior leg muscles. Quantitative electromyography and histologic findings revealed neurogenic features not only in the affected legs, but also in clinically uninvolved limbs. Monomelic amyotrophy of lower limb is a variant of spinal muscular atrophy with a benign course. However, as in the early stages of the disease there are no distinctive clinical or laboratory findings with other motor neuron diseases, the diagnosis of monomelic amyotrophy may be made only retrospectively after a prolonged observation.

Linkage analysis of distal hereditary motor neuropathy type II (distal HMN II) in a single pedigree

We describe a six generation family affected with the autosomal dominant form of distal hereditary motor neuropathy type II (distal HMN II). The distal HMN shows similarities with the hereditary motor and sensory neuropathies type I and II (HMSN I and HMSN II) or Charcot-Marie-Tooth disease type 1 and 2 (CMT 1 and CMT 2) and with some proximal HMN or spinal muscular atrophies (SMA). Gene loci have been assigned to chromosomes 1q, 17p, and 19q for CMT 1 and to chromosome 5q for recessive SMA. In this study we excluded all four regions for the presence of distal HMN II, indicating that this neuropathy is genetically different from CMT 1 and recessive SMA.

Segmental spinal muscular atrophy and dermatological findings in a patient with chromosome 18q deletion

We have evaluated a young woman with segmental spinal muscular atrophy, who has a deletion of a portion of the long arm of chromosome 18. She also has vitiligo and lichen sclerosis et atrophicus. She has neither the facial dysmorphism nor the mental deficit usually associated with the 18q- syndrome. Magnetic resonance imaging scan of her brain demonstrates high signal intensity consistent with abnormal myelination. Southern blot analysis of her DNA demonstrates that the deletion includes the gene for human myelin basic protein. Neither spinal muscular atrophy nor this patient's skin manifestations have been previously reported in association with 18q-.

Sensory axonopathy in hereditary distal spinal muscular atrophy

A girl of 14 year is presented with a distal spinal muscular atrophy (SMA) with autosomal recessive inheritance. The technical findings are in agreement with the diagnosis. Light microscopical examination of sural nerve biopsy, including teased fiber studies and morphometry, showed no abnormalities. Electron microscopical investigation however demonstrated axonal pathology. The question arises if distal SMA is a distal axonopathy mainly of motor nerves, but to some extent also of sensory nerves.

Polyneuropathies in paediatrics

Non-acute polyneuropathies (PNPs) encountered in paediatrics are reviewed. Emphasis is placed on three main groups of conditions: the relatively rare but treatable dysimmune PNP (chronic relapsing dysimmune polyneuropathies, CRDP); the more common hereditary motor/sensory neuropathies (HMSN and HSN); and the often missed symptomatic neuropathies of some heredodegenerative and neurometabolic disorders. Diagnostic procedures are discussed. One conclusion drawn is that so far metabolic screening procedures do not give any diagnostic or aetiological information in HMSN or in HSN, nor in heredoataxias or heredoparaplegias. When a specific neurometabolic disease is suspected from the clinical symptomatology, individually structured investigations are necessary.

Distal infantile spinal muscular atrophy associated with paralysis of the diaphragm: a variant of infantile spinal muscular atrophy

We report the clinical, electrophysiological, and morphological observations of five infants with an unusual form of spinal muscular atrophy (SMA). In these infants muscular weakness and atrophy were initially restricted to the distal limbs and this pattern was associated with paralysis of the diaphragm. The difference between the clinical manifestations of this syndrome and the classical form of infantile spinal muscular atrophy (SMA type 1) as well as other congenital hereditary neuropathies is discussed.

Hereditary distal muscular atrophy with vocal cord paralysis and sensorineural hearing loss: a dominant form of spinal muscular atrophy?

In 1980 Young and Harper described a family with an unusual form of distal spinal muscular atrophy associated with vocal cord paralysis. We report a family with three similarly affected subjects. Progressive sensorineural hearing loss was an additional feature in our patients. Electrophysiological and histological investigations did not exclude an involvement of sensory neurones. Whether the classification of this dominant disorder with the spinal muscular atrophies is justified will depend on additional studies in further families.

A follow-up study of 60 cases of chronic spinal muscular atrophy

60 cases of chronic spinal muscular atrophy (CSMA) were followed-up for a period varying from 5 to 40 years. The neuromuscular impairment was evaluated by Norris' ALS score, both at the time of last examination and retrospectively at the time of diagnosis. Age at onset of symptoms was the most important factor in the progression of the neuromuscular damage. Monomelic or asymmetric location of symptoms at the time of diagnosis and duration of the disease were not significantly correlated to the worsening of ALS score.

Prevalence of hereditary motor and sensory neuropathy in Cantabria

One hundred and forty-four patients with hereditary motor and sensory neuropathy (HMSN) were selected from within a defined area (Cantabria) in Northern Spain, from 1974 to 1984. The series comprises 49 index cases and 95 affected relatives. The prevalence ratio was 28.2 cases per 100,000. The results of the study indicate that the majority of the cases were hereditary as a dominant trait. The prevalence for the Type I HMSN cases did not differ from that of Type II cases. Previous population-surveys of these disorders are compared.

Hereditary motor neuropathy, distal type: electrophysiological and pathological studies of a case

A case of HMN, distal type transmitted as autosomal dominant is described. Clinical findings appear to be consistent with a peroneal muscular atrophy, indistinguishable from HMSN types I and II. The electrophysiological data reveal a pathological involvement of the anterior horns, whereas sensory and motor conduction are normal. A muscle biopsy showed neurogenic atrophy, while the morphology of the sural nerve was normal.

A dominantly inherited lower motor neuron disorder presenting at birth with associated arthrogryposis

Of a family consisting of 54 members, 44 were examined. Twenty-one showed signs of a clinically non-progressive congenital lower motor neuron disorder restricted to the lower part of the body, which resulted in arthrogryposis in 15 cases. The mode of inheritance is autosomal dominant with very varied expression of the gene.

Amyotrophic lateral sclerosis: Part 1. Clinical features, pathology, and ethical issues in management

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease of the motor system in adults that occurs in sporadic, familial, and Western Pacific forms. Involvement of non-motor pathways has been increasingly recognized, both clinically and pathologically. Although the usual course is relentlessly progressive with death in half the cases within three years from onset, it can sometimes be protracted. Degeneration and loss of large motor neurons in the cerebral cortex, brainstem, and cervical and lumbar spinal cord are characteristic. Marked reduction in the number of large myelinated fibers is notable in the cervical and lumbar ventral roots. Peripheral nerves show reduced numbers of large myelinated fibers, acute axonal degeneration at all levels, and distal axonal atrophy. Motor end-plates reveal small or absent nerve terminals. Subclinical non-motor system involvement includes neuronal loss in Clarke's nucleus and dorsal root ganglia, degeneration of non-motor tracts in the spinal cord, loss of receptors in the dorsal horns of the spinal cord, and myelinated fiber loss with segmental demyelination in sensory and mixed nerves. The serious implications of the diagnosis of ALS make it mandatory to exclude similar potentially treatable disorders. Management should be multidisciplinary, and discussions with the patient and family members should be frank and frequent. Discussions about ventilatory support should take place early in the disease so that death from respiratory failure can be prevented, when that is desired, and conversely to obviate the discontent and anger that accompany involuntary life on a ventilator.

Chronic proximal spinal muscular atrophy of childhood and adolescence: sex influence

Segregation analysis was performed on 354 cases of chronic proximal spinal muscular atrophy of childhood and adolescence (CPSMA) in the total series and in a number of subgroups formed according to the age at onset and sex. The analysis provided evidence of sex influence in the series studied, particularly in a subgroup of the milder form of the disease with onset between the 37th month and 18th year of life. In the latter subgroup, females were affected much less frequently. This was particularly striking after age at onset of 8 years, and only exceptionally were females affected after the age of 13 years. These facts point to incomplete penetrance of the gene.

Peroneal muscular atrophy. Part 1. Clinical and electrophysiological study

144 patients with the clinical syndrome of peroneal muscular atrophy or Charcot-Marie-Tooth disease were studied. Thirteen were recognized as the spinal form of the disease since all had normal motor nerve conduction velocity and sensory nerve action potential. The remaining patients could be classified according to their values of motor conduction velocity for the median nerve. Two main groups were therefore identified: 55 patients whose nerve conduction was below 30 m/s belonged to group I, which corresponds to the previously reported hypertrophic form or hereditary motor sensory neuropathy (HMSN) type I. Sixty-four patients whose nerve conduction was above 40 m/s belonged to group II which corresponds in the majority of cases to the neuronal form or HMSN type II. Twelve patients could not be classified since the motor nerve conduction velocity for median nerve ranged between 30 and 40 m/s. These could belong to either of the two main groups or might form an intermediate group, the existence of which is discussed. Clinical genetic and electrophysiological features of the two main groups are discussed and compared.

Hereditary motor and sensory neuropathies in Swedish children. II. Neuronal-axonal types

Clinical, neurophysiological and laboratory data are given for 32 children (30 kinships) considered to represent hereditary motor and sensory neurophaties (HMSN) of neuronal-axonal types. In 25 families (27 cases) one of the parents was found to be affected. In one both parents were normal. The mode of inheritance in the 27 patients with familial neuronal-axonal HMSN was concluded to be autosomal dominant HMSN II (Lambert type). The disability was mild to moderate and, on an average, less pronounced than in de- and remyelinating types of HMSN. Seven out of 27 were early toe-walkers of the secondary type. Cavus feet were noted in 25, hand atrophies in eight and mild scoliosis in five. Sensory complaints were recorded in 21. The nerve conduction velocities (NCVm and NCVs) of children and parents were slightly subnormal in a few. EMG proved to be the most important parameter for identifying subclinically affected parents.

The nosology of genetic peripheral neuropathies in Swedish children

103 consecutive childhood cases of genetic peripheral neuropathies of heredodegenerative background were collected from Gothenburg from 1973 to 1980. From this series, 63 hereditary motor and sensory neuropathies (HMSN) were distinguished: 31 cases of demyelinating and remyelinating HMSN (HMSN I), 21 (18 families) with an autosomal dominant and 10 with sporadic mode of inheritance and unaffected parents; and 32 cases of neuronal-axonal types (HMSN II), 27 of whom (25 families) had at least one affected, if asymptomatic, parent. In one family, both parents were neurologically and neurophysiologically completely normal. Three cases of uncharacteristic HSN were diagnosed. Among 37 cases with a combined degenerative encephalopathy/myelopathy and a peripheral neuropathy, nine had hereditary spastic paraplegia, six had heredoataxias (three of the Friedreich type), nine had lysosomal storage diseases (five of the Krabbe type), seven had other known inborn metabolic errors and six had biochemically undefined disorders. Progressive neuropathies are important manifestations of a large variety of genetically determined heredodegenerative neurological disorders of infancy and childhood. For classification of HMSN, clinical and neurophysiological examinations are necessary for the index case and for both parents as well.

A clinico-pathological study of chronic hereditary motor neuropathy

Forty cases of chronic hereditary motor neuropathy (CHMN) were divided into five categories according to the distribution of muscle atrophy; they were proximal, facioscapulohumeral, bulbospinal, distal and scapuloperoneal forms. Their clinical features and laboratory data were analysed, and muscle biopsies from 32 of them were studied by histological, histochemical and electron microscopical methods. An attempt at quantitative assessment of the histological changes was also made. All muscle biopsies showed a mixture of neurogenic and 'myopathic' changes in varying proportions. They showed more 'myopathic' changes than Werdnig-Hoffmann's disease, amyotrophic lateral sclerosis and other neurogenic atrophies except Charcot-Marie-Tooth disease. There was marked variation in the average number of atrophied muscle fibers contained in grouped atrophy. Frequently, deranged internal structure of the muscle fibres was revealed both by histochemical and electron microscopical methods. Based on the evidence of heterogeneity of CHMN in respect of genetics, clinical features and histological changes, it was speculated that CHMN represents a group of diseases which involves primarily different parts of the motor units.

X-linked adult form of spinal muscular atrophy

Neurological and endocrinological studies were carried out in 8 of 12 male patients with X-linked spinal muscular atrophy. In six investigated cases, gynaecomastia was discovered. First muscle symptoms started between 21 and 44 years of age, at which time the patients observed disturbances in their sexual life. In three cases decreased fertility and in two cases sterility was reported. Diagnostic testicular biopsy showed pronounced involutional changes of the Leydig cells. The plasma testosterone level was decreased, while the levels of luteinizing hormone and prolactine were normal, and the follicle stimulating hormone was at a high normal level. The dexamethasone/human chorionic gonadotrophin test revealed a pronounced decrease in the functional reserve of the Leydig cells. It is suggested that all these anomalies are connected with an increased ratio of oestrogen to androgen level.

X-linked recessive bulbospinal neuronopathy: a report of ten cases

A form of adult onset 'bulbospinal muscular atrophy' of X-linked recessive inheritance is described in 10 patients from eight families. Muscle weakness in the limbs was mainly proximal and developed in the third to fifth decades of life, often preceded by muscle cramps on exertion and tremor of the hands. Weakness and fasciculation of the facial muscles and tongue were prominent. All the patients had gynaecomastia and some were infertile. Two had diabetes mellitus. Motor nerve conduction studies were normal but most patients had small or unrecordable sensory action potentials in the absence of clinical sensory loss. Plasma creatine kinase levels were considerably elevated and muscle biopsies showed neurogenic atrophy together with secondary myopathic changes. The importance of recognising this distinctive disorder in single cases (six of the present series) is emphasised.

The distal form of spinal muscular atrophy: an unusual case demonstrating the intermediate variety

A 14-year-old boy with a long history of distal muscle weakness affecting primarily and predominantly the upper limbs is described. There is a family history of pes cavus and congenital dislocation of the hip. Electromyography and histopathological studies of skeletal muscle showed conclusive evidence of a neurogenic muscular disorder, and excluded primary muscle disease. The muscle biopsy showed group atrophy. As many target fibres which are identical to structured cores were a prominent feature of the biopsy, central core disease was considered. However, it was concluded on clinical, neurophysiological and histological evidence that the patient was suffering from distal spinal muscular atrophy of an intermediate type designated by previous authors.

A review of the current concepts of distal muscle weakness is included.

Linkage of autosomal dominant type I hereditary motor and sensory neuropathy to the Duffy locus on chromosome 1

Data from English families confirms the probable linkage of the loci for autosomal dominant type I hereditary motor and sensory neuropathy (HMSN) and the Duffy blood group. The locus for autosomal dominant type I HMSN is in chromosome 1 near the centromere, about 15 centimorgans from the Duffy locus. The linkage between type I HMSN and the Duffy locus and the two recombinants found between Duffy and type II HMSN support the hypothesis that there are at least two genetic variants of autosomal dominant HMSN.

Genetic aspects of hereditary motor and sensory neuropathy (types I and II)

The genetic features of a series of 227 patients with hereditary motor and sensory neuropathy (HMSN) have been analysed. The series comprised 119 index cases from 110 families in which 108 affected relatives were identified. The cases were classified as having type I or type II HMSN on the basis of nerve conduction studies. Inheritance in the type I cases was autosomal dominant in 139 (45 families) and autosomal recessive in eight (four families) with 26 single cases. For the type II cases, 35 (17 families) were autosomal dominant and three (two families) autosomal recessive with 16 single cases. A significant excess of males was present in the combined single and recessive type I cases and in the type I index cases. No X linked pedigrees were identified.

The correlation coefficients for motor nerve conduction velocity between the index cases and their relatives suggested further genetic heterogeneity in the type I cases. Parent-offspring and sib-sib correlation coefficients for age of onset in the dominantly inherited type I cases were less than 0·5. There was therefore no strong suggestion of genetic heterogeneity in terms of age of onset.

The severity of muscle weakness did not differ between the dominantly inherited type I and type II cases. In both types males had higher weakness scores than females, but there was no difference for either type in relation to the sex of the affected parent.

Segration analysis suggested that approximately 70% of the single generation type I cases were of autosomal recessive inheritance, whereas only about 25% of the single generation type II cases were recessive. Biological fitness was reduced in type II HMSN, which would support a higher proportion of new dominant mutations among the single cases of this type than in type I. Despite the excess of males in the type I single case/recessive category, a contribution of cases with X linked recessive inheritance is improbable. Single cases of HMSN, especially the type II form in view of its later onset, are likely to be unrecognised clinically and will be classified as `cryptogenic' neuropathy. As in many affected subjects the degree of disability is minimal, a careful scrutiny of the relatives is merited in such instances.