Autosomal recessive inheritance of hereditary motor and sensory neuropathy with optic atrophy.

Three siblings are reported with childhood onset hereditary motor and sensory neuropathy (HMSN) and adult onset optic atrophy. Electrophysiological studies showed an axonal neuropathy and dysfunction of the retinal ganglion cells or optic nerve. The presumed mode of inheritance is autosomal recessive. This is the second family in which autosomal recessive inheritance of HMSN and optic atrophy (HMSN type VI) has been described, and the first in which electrophysiological studies have been reported.     

Hereditary motor and sensory neuropathy with absence of large myelinated fibers due to absence of large neurons in dorsal root ganglia and anterior horns, clinically associated with deafness, mental retardation, and epilepsy (HMSN-ADM)

Hereditary motor and sensory neuropathy (HMSN) with autosomal recessive inheritance represents a genetically heterogeneous group of disorders with variable clinical, pathologic and electrophysiologic manifestations. A new variant of autosomal recessive HMSN, clinically defined by sensorimotor polyneuropathy associated with deafness and mental retardation, has recently been described. We report on the first autopsy case with this type of HMSN: a girl of non-consanguineous parents with a presumably autosomal recessive type of motor and sensory neuropathy clinically associated with deafness, mental retardation, and epilepsy. The autopsy showed complete absence of large myelinated fibers in peripheral motor and sensory nerves corresponding to a lack of large neurons in dorsal root ganglia and anterior horns of the spinal cord, moderate neurogenic muscle atrophy, and nearly complete absence of neurons in the dentate nucleus of the cerebellum. Molecular genetic analyses in our case revealed neither genetic alterations in the survival motor neuron gene nor in the PMP-22 gene.     

Hereditary motor and sensory neuropathy with diaphragm and vocal cord paresis

We describe two kindreds with an autosomal dominant inherited disorder characterized by a variable degree of muscle weakness of limbs, vocal cords, and intercostal muscles and by asymptomatic sensory loss, beginning in infancy or childhood in severely affected persons. Life expectancy in severely affected patients is shortened because of respiratory failure. Because nerve conduction velocities are normal and it is an inherited axonal neuropathy, we classify the disorder as a variety of hereditary motor and sensory neuropathy type II (HMSN II) (HMSN IIc). The present report provides further evidence for heterogeneity among the hereditary motor and sensory neuropathy type II disorders. In one large pedigree with the type IIc disorder, no linkage to DNA markers known to map near the HMSN IA locus on chromosome 17p or the HMSN IB locus on chromosome 1q was demonstrated.     

Autosomal recessive forms of hereditary motor and sensory neuropathy.

Six families are described with hereditary motor and sensory neuropathy (HMSN) of probable autosomal recessive inheritance. Four of these were classified as HMSN type I and two as type II. The consanguinity rate in this series was high, suggesting that these recessive genes are rare. In comparison with the dominantly inherited forms of these disorders, the mean age of onset was significantly earlier for the type II cases but did not differ for the type I patients. Motor nerve conduction velocity was significantly less for the type I cases but did not differ for the type II form. The recessive type I cases tended to show a greater incidence of weakness, ataxia, tendon areflexia and scoliosis than in the dominant form. The importance of differentiating such cases from Friedreich''s ataxia is emphasised.     

Homozygous hypertrophic hereditary motor and sensory neuropathies

We compared 25 autosomal dominant hereditary motor and sensory neuropathy (HMSN) type I patients with 7 subjects affected by hypertrophic HMSN with non-dominant inheritance. All the autosomal dominant HMSN I cases carried the chromosome 17p11.2 duplication, providing evidence that it is widely represented in HMSN I families. The second group included: Two siblings born to unrelated, unaffected parents and suffering from hypertrophic HMSN of strikingly different severity; two sisters with HMSN I phenotype, born to first-cousin unaffected parents; two brothers with HMSN III phenotype born to unrelated parents both showing HMSN II phenotype; a child with classic HMSN III phenotype, born to unrelated, unaffected parents. The 17p11.2 duplication was not found in any of the patients of the second series or in their parents. Our data provide further evidence that: HMSN III is heterogeneous and encompasses the homozygous expressions of different neuropathic genes; it is advisable to separate autosomal recessive hypertrophic HMSN from dominant HMSN Ia, because they appear to be due to different DNA mutations. DNA analyses were supported by grants from P.F. Biotecnologie CNR, Telethon, Murst 40% and 60%.     

Varying occurrence of vocal cord paralysis in a family with autosomal dominant hereditary motor and sensory neuropathy

A white British family with the axonal form of hereditary motor and sensory neuropathy (HMSN, type II) contained one member who developed a recurrent laryngeal nerve palsy at the age of 41 years, in addition to 4 years of symptomatic polyneuropathy and an abducens nerve palsy. Neither of the other family members (the mother and sister) with electrophysiologically confirmed polyneuropathy had any neuropathic symptoms in the limbs or laryngeal or respiratory muscle involvement. An autosomal dominant pattern of inheritance is likely. This is a second report of this rare form of HMSN (type IIC) in which there is associated laryngeal or respiratory muscle weakness. This family differs from the two previously reported pedigrees in which laryngeal or diaphragm weakness had commenced within the first two decades. The discovery of asymptomatic family members attests to the diagnostic value of clinical and electrophysiological study of first-degree relatives when laryngeal or bulbar symptoms develop in the context of chronic axonal polyneuropathy. HMSN type IIC should be distinguished from the more common forms of HMSN – type IIA, in which axonal polyneuropathy is restricted to the limbs, and type IIB, which is of early onset and associated with foot ulceration. Received: 10 July 1998 Received in revised form: 8 December 1998 Accepted: 10 December 1998     

Hereditary motor and sensory neuropathy with myelin folding and juvenile onset glaucoma

OBJECTIVE: We describe three patients from a family with motor and sensory neuropathy accompanied by open-angle glaucoma. BACKGROUND: Autosomal recessive demyelinating hereditary motor and sensory neuropathies (HMSN) include different disorders. To our knowledge, autosomal recessive HMSN has not been associated with juvenile onset glaucoma. METHODS: Sural nerve pathology of the three patients were examined, and genetic analysis of the family was performed. Result:- The most prominent pathologic finding was a highly unusual myelin abnormality consisting of irregular redundant loops and folding of the myelin sheath. The family survey supports autosomal recessive inheritance. The molecular analysis failed to demonstrate either linkage of the disease to MPZ gene, PMP22 gene, Cx32 gene, orEGR2 gene. Analysis did not establish linkage of the disease to the locus of CMT4A, 4B, and 4C genes. CONCLUSION: The present cases may represent a new type of HMSN accompanied by juvenile onset glaucoma.     

AAEE case report #20: hereditary motor and sensory neuropathy, type I

A case study is reported regarding a 32-year-old man with classic clinical and electrophysiologic features of hereditary motor and sensory neuropathy, type I (HMSN I), a slowly progressive autosomal dominant condition marked by slow motor and sensory velocities and generalized segmental demyelination. Another clinically similar autosomal dominant neuropathy (HMSN II) is distinguished from HMSN I by nearly normal nerve conduction velocity. Acquired demyelinating neuropathy may occasionally resemble HMSN I clinically, but the former demonstrates electrophysiologic features not seen in the latter such as conduction block, dispersed compound muscle action potentials, and differential slowing of conduction velocity. Neuropathologic studies of HMSN I suggest that both neuronal and Schwann cell distrubances play a role in pathogenesis.     

HMSN III phenotype due to homozygous expression of a dominant HMSN II gene.

We describe two siblings with hereditary motor and sensory neuropathy (HMSN) type III. Their parents were both affected with autosomal dominant axonal HMSN. The neuropathy in the siblings probably resulted from homozygous expression of the HMSN II gene. Together with other reports of homozygous HMSN I, this family suggests that HMSN III is heterogenous and encompasses the most severe homozygous expression of neuropathic genes.     

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.     

A novel type of hereditary motor and sensory neuropathy characterized by a mild phenotype.

BACKGROUND: Three loci for autosomal dominant hereditary motor and sensory neuropathy type I (HMSN I) or Charcot-Marie-Tooth disease type 1 (CMT1) have been identified on chromosomes 17p11.2 (CMT1A), 1q21-q23 (CMT1B), and 10q21.1-q22.1 (designated here as CMT1D). The genes involved are peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ), and the early growth response element 2 (EGR2), respectively. Probably a fourth locus (CMT1C) exists since some autosomal dominant HMSN I families have been excluded for linkage with the CMT1A and CMT1B loci. Four loci for autosomal dominant hereditary motor and sensory neuropathy type II (HMSN II) or Charcot-Marie-Tooth disease type 2 (CMT2) have been localized on chromosomes 1p35-p36 (CMT2A), 3q13-q22 (CMT2B), 7p14 (CMT2D), and 3p (HMSN-P). OBJECTIVE: To describe the clinical, electrophysiologic, and neuropathological features of a novel type of Charcot-Marie-Tooth disease. PATIENTS AND METHODS: We performed linkage studies with anonymous DNA markers flanking the known CMT1 and CMT2 loci. Patients and their relatives underwent clinical neurologic examination and electrophysiologic testing. In the proband, a sural nerve biopsy specimen was examined. RESULTS: Linkage studies excluded all known CMT1 and CMT2 loci. The clinical phenotype is mild and almost all affected individuals remain asymptomatic. Electrophysiologic and histopathological studies showed signs of a demyelinating neuropathy, but the phenotype is unusual for either autosomal dominant HMSN I or HMSN II. CONCLUSION: Our findings indicate that the HMSN in this family represents a novel clinical and genetic entity.     

Clinical and pathological features of an autosomal recessive neuropathy

Two siblings are described, ages 49 and 45 years, having a distinct hereditary motor and sensory neuropathy (HMSN) with severe peroneal nerve involvement. The neuropathic symptoms began in childhood. Both patients have sensorineural deafness. The proband was found to have a cardiac conduction abnormality in the absence of known ischemic heart disease. Electrodiagnostic studies were consistent with a demyelinating peripheral neuropathy. The presence of parental consanguinity and absence of affected individuals in succeeding or preceding generations suggested that the sensorimotor neuropathy in this family is inherited in an autosomal recessive manner. The sural nerve of the proband had significant loss of myelinated fibers and demyelination but few regenerating myelinated fibers and no onion-bulbs. The pathological findings, while nonspecific, are not characteristic of the hypertrophic, neuronal or intermediate types of HMSN.     

Autosomal recessive form of hereditary motor and sensory neuropathy type I.

We studied pathologic changes in sural nerve biopsies from four patients with probable autosomal recessive (AR) hereditary motor and sensory neuropathy (HMSN) type I with a median motor nerve conduction velocity greater than 10 m/sec, comparing them with the pathologic features in autosomal dominant (AD) HMSN type I. The four recessive and two sporadic cases showed segmental demyelination. However, the classic onion bulbs of concentric Schwann cell processes, which occur in AD type I, were rare; many axons, also of a smaller size, were surrounded by onion bulbs of basal laminae. Schwann cells of the myelinated and unmyelinated types were involved in these onion bulb formations. Patients with HMSN type I who have many basal lamina onion bulbs should be considered as having AR inheritance.     

Axonal neuropathy with optic atrophy is caused by mutations in mitofusin 2

OBJECTIVE: Charcot-Marie-Tooth (CMT) neuropathy with visual impairment due to optic atrophy has been designated as hereditary motor and sensory neuropathy type VI (HMSN VI). Reports of affected families have indicated autosomal dominant and recessive forms, but the genetic cause of this disease has remained elusive. METHODS: Here, we describe six HMSN VI families with a subacute onset of optic atrophy and subsequent slow recovery of visual acuity in 60% of the patients. Detailed clinical and genetic studies were performed. RESULTS: In each pedigree, we identified a unique mutation in the gene mitofusin 2 (MFN2). In three families, the MFN2 mutation occurred de novo; in two families the mutation was subsequently transmitted from father to son indicating autosomal dominant inheritance. INTERPRETATION: MFN2 is a mitochondrial membrane protein that was recently reported to cause axonal CMT type 2A. It is intriguing that MFN2 shows functional overlap with optic atrophy 1 (OPA1), the protein underlying the most common form of autosomal dominant optic atrophy, and mitochondrial encoded oxidative phosphorylation components as seen in Leber's hereditary optic atrophy. We conclude that autosomal dominant HMSN VI is caused by mutations in MFN2, emphasizing the important role of mitochondrial function for both optic atrophies and peripheral neuropathies.     

Peroneal muscular atrophy with pyramidal features.

Twenty-five cases of peroneal muscular atrophy with pyramidal features from 15 families are described. This disorder has been referred to as hereditary motor and sensory neuropathy (HMSN) type V by Dyck. Onset was usually in the first two decades of life with difficulty in walking. The clinical syndrome superficially resembled that of HMSN types I and II with distal wasting and weakness involving the legs more than the arms. The tendon reflexes in the upper limbs and at the knee tended to be normal or increased but the ankle jerks were often absent. The plantar responses were extensor in 22 patients, absent in two and flexor in one. Increased tone and weakness in the proximal lower limb muscles were found in about 30% of cases. Mean motor nerve conduction velocity was lower than in normal controls and sensory nerve action potentials were reduced in amplitude or absent in two thirds of the patients studied. Inheritance was autosomal dominant in the majority of families. The disorder was slowly progressive but did not lead to severe disability.     

Hereditary motor sensory neuropathy type II with neurofilament accumulaion: New finding or new disorder?

Peroneal muscular atrophy is now known to be heterogeneous and to be due to various underlying genetic mechanisms. Exploring this heterogeneity further, we report on a German kinship with the clinical, genetic, and nerve conduction features of hereditary motor and sensory neuropathy type II (HMSN type II) but whose sural nerves on biopsy were found to show infrequent axonal swellings with neurofilament accumulations not previously described. The dominant inheritance and absence of kinky hair set this disorder apart from giant axonal neuropathy. There was no history of toxic exposure to industrial chemicals. We conclude that the disorder either is a new type of HMSN or is HMSN type II with previously unencountered neurofilament accumulations. Neurofilament accumulation indicates that the axon could be a site for primary derangement and may implicate an abnormality of slow axonal flow. In addition, some of the patients exhibited features suggestive of a cardiomyopathy.     

Hereditary auditory, vestibular, motor, and sensory neuropathy in a Slovenian Roma (Gypsy) kindred.

Members of a Roma (Gypsy) family with hereditary motor and sensory peripheral neuropathy (HMSN) and concomitant auditory and vestibular cranial neuropathies were identified in Kocevje, Slovenia. The illness begins in childhood with a severe and progressive motor disability and the deafness is delayed until the second decade. There are no symptoms of vestibular dysfunction. The family structure is consistent with an autosomal recessive pattern of inheritance and the genetic locus for the disorder is linked to the same region of chromosome 8q24 as other Roma families with HMSN and deafness from Lom, Bulgaria (HMSN-Lom). The present study shows that the deafness is caused by a neuropathy of the auditory nerve with preserved measures of cochlear outer hair cell function (otoacoustic emissions and cochlear microphonics) but absent neural components of auditory brainstem potentials. The hearing loss affects speech comprehension out of proportion to the pure tone loss. Vestibular testing showed absence of caloric responses. Physiological and neuropathological studies of peripheral nerves were compatible with the nerve disorder contemporaneously affecting Schwann cells and axons resulting in both slowed nerve conduction and axonal loss. Genetic linkage studies suggest a refinement of the 8q24 critical region containing the HMSN-Lom locus that affects peripheral motor and sensory nerves as well as the cranial auditory and vestibular nerves.     

Hereditary motor and sensory neuropathy of neuronal type with onset in early childhood

Eleven cases of a severe neuropathy with onset in early childhood are described. The condition commences with distal weakness and wasting of the lower limbs and subsequently involves the hands, causing severe paralysis of the hands and feet towards the end of the second decade. Sensory changes are common but are usually only mild. The peripheral nerves are not enlarged. Claw hand, scoliosis and other orthopaedic deformities are seen in the later stages. CSF protein is not elevated and there is only mild slowing of motor conduction velocities. The pathological changes in sural nerve biopsies are those of axonal degeneration affecting myelinated and unmyelinated fibres. Family studies suggested autosomal recessive inheritance in two kindreds and dominant inheritance in another. Five cases were sporadic. The condition is clinically more severe and of earlier onset than hereditary motor and sensory neuropathy (HMSN) type II and differs electrophysiologically and pathologically from Déjerine-Sottas disease.     

Autosomal dominant optic atrophy with asymptomatic peripheral neuropathy.

The association between hereditary motor and sensory neuropathy (HMSN) and optic atrophy has been termed HMSN type VI. The autosomal dominant inheritance of this syndrome is reported. Three generations were affected with optic atrophy, which differed in some respects from classic dominant optic atrophy, and an asymptomatic, mainly sensory, neuropathy.     

Hereditary motor and sensory neuropathy-russe: new autosomal recessive neuropathy in Balkan Gypsies

A novel peripheral neuropathy of autosomal recessive inheritance has been identified in Balkan Gypsies and termed hereditary motor and sensory neuropathy-Russe (HMSN-R). We investigated 21 affected individuals from 10 families. Distal lower limb weakness began between the ages of 8 and 16 years, upper limb involvement beginning between 10 and 43 years, with an average of 22 years. This progressive disorder led to severe weakness of the lower limbs, generalized in the oldest subject (aged 57 years), and marked distal upper limb weakness. Prominent distal sensory loss involved all modalities, resulting in neuropathic joint degeneration in two instances. All patients showed foot deformity, and most showed hand deformity. Motor nerve conduction velocity was moderately reduced in the upper limbs but unobtainable in the legs. Sensory nerve action potentials were absent. There was loss of larger myelinated nerve fibers and profuse regenerative activity in the sural nerve. HMSN-R is a new form of autosomal recessive inherited HMSN caused by a single founder mutation in a 1 Mb interval on chromosome 10q.