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Minifascicular neuropathy (MN) is a rare, autosomal recessive disease with prominent structural changes of peripheral nerves. So far, it has been observed in females with a 46,XY karyotype and mutations of the Desert Hedgehog (DHH) gene, thus linking MN to gonadal dysgenesis (GD) and disorders of sex development (DSD). However, a 46,XX proband with normal female sex and gender development underwent clinical evaluations, nerve conduction studies and genetic screening for a severe motor-sensory neuropathy with a pathological phenotype that hinted at MN. Indeed, sural nerve biopsy revealed a profound disturbance of perineurium development with a thin and loose structure. High-resolution ultrasound (HRUS) also disclosed diffuse changes of nerve echotexture that visibly correlated with the pathological features. After extensive genetic testing, a novel homozygous DHH null mutation (p.Ser185*) was identified in the proband and in her sister, who was affected by a similar motor-sensory neuropathy, but was eventually found to be a 46,XY patient according to a late diagnosis of DSD with complete GD. DHH should therefore be considered as a possible cause of rare non-syndromic hereditary motor-sensory neuropathies, regardless of DSD. Furthermore, HRUS could effectively smooth the complex diagnostic workup as it demonstrated a high predictive power to detect MN, providing the same detailed correlations to the pathologic features of the nerve biopsy and Dhh-/- mice in both sisters. Hence, HRUS may assume a pivotal role in guiding molecular analysis in individuals with or without DSD., (© 2020 Peripheral Nerve Society.)

To identify novel mutations causing hereditary motor and sensory neuropathy (HMSN) with pyramidal signs, a variant of Charcot-Marie-Tooth disease (CMT), we screened 28 CMT and related genes in four members of an affected Japanese family. Clinical features included weakness of distal lower limb muscles, foot deformity, and mild sensory loss, then late onset of progressive spasticity. Electrophysiological studies revealed widespread neuropathy. Electron microscopic analysis showed abnormal mitochondria and mitochondrial accumulation in the neurons and Schwann cells. Brain magnetic resonance imaging (MRI) revealed an abnormally thin corpus callosum. In all four, microarrays detected a novel heterozygous missense mutation c.1166A>G (p.Y389C) in the gene encoding the light-chain neurofilament protein (NEFL), indicating that NEFL mutations can result in a HMSN with pyramidal signs phenotype., (© 2015 Peripheral Nerve Society.)

Transthyretin-related familial amyloidotic polyneuropathy (TTR-FAP) usually presents itself as a progressive sensorimotor polyneuropathy with severe autonomic dysfunction and cardiomyopathy. Eighteen patients carrying the Leu64 mutation underwent a series of regular follow-ups, including: neurological examination, electroneurography, electromyography, electrocardiography and echocardiography, blood analysis, a questionnaire on autonomic symptoms, cardiovascular autonomic tests and a 99mTc-DPD examination study. A late onset of a slowly progressive disease which reached its terminal stage after about 10  years was observed. The onset was mainly a length-dependent sensory neuropathy, although a focal onset with carpal tunnel syndrome was detected in three patients. At the onset of the disease, autonomic dysfunction was present in a small number of patients, but, within a few years, this had manifested in all members of the sample group. The only extra-neurological manifestations were cardiac related. It is reasonable to consider Southern Italy as an endemic focus of TTR-FAP. An underestimation of disease prevalence could be caused by a late onset of FAP, which can manifest in patients up to their late 70s. Follow-up of asymptomatic individuals may permit the early detection of symptoms and signs, allowing a detailed record of the natural history of the disease from the beginning and facilitating prompt treatment., (© 2012 Peripheral Nerve Society.)

The infantile-onset axonal neuropathies and neuronopathies are an uncommon and heterogeneous group of conditions causing weakness, wasting, and developmental delay in early childhood. Many are associated with central nervous system or other systemic manifestations and cause early mortality. We review the axonal Charcot-Marie-Tooth subtypes with onset in infancy, spinal muscular atrophy, and related syndromes of early infancy, giant axonal neuropathy, infantile neuroaxonal dystrophy, hereditary motor and sensory neuropathy with agenesis of the corpus callosum, early-onset neuropathies associated with mitochondrial disorders, and other less well-delineated clinical entities. Useful clinical and neuropathologic features in the diagnostic work-up of these conditions are also presented., (© 2012 Peripheral Nerve Society.)

Point mutations in PMP22 are relatively rare and the phenotype may vary from mild hereditary neuropathy with liability to pressure palsies (HNPP) to severe Charcot-Marie-Tooth type 1 (CMT1). We describe the phenotype of the Gly94fsX222 mutation in the PMP22 gene. Medical records of all patients were reviewed and 11 patients were re-examined. EMG was carried out in nine patients and nerve biopsy in one. Thirteen patients originating from seven families with a Gly94fsX222 mutation were included and consisted of 10 women and 3 men with a median age of 41 years (range 7-67). Five index patients were originally suspected of CMT1. Ten patients had abnormal motor skills during childhood. Nine patients had a history of pressure palsies. Involvement of the olfactory, trigeminal, facial, and pudendal nerves occurred in three patients. Twelve patients had pes cavus and one scoliosis. Distal anterior leg and distal arm weakness were found in 12 and 4 patients, respectively. Twelve patients had distal leg sensory abnormalities. Electrophysiological examination revealed a demyelinating sensorimotor neuropathy, both resembling CMT1 and HNPP. Sural nerve biopsy showed demyelinating neuropathy with presence of tomacula. More than three-fourths of the patients with Gly94fsX222 mutation demonstrated a CMT1 phenotype combined with transient deficits. Clinicians should test for this mutation in those patients exhibiting a generalised neuropathy combined with compressive like episodes., (© 2011 Peripheral Nerve Society.)

Charcot-Marie-Tooth disease type 1B (CMT1B) and Déjerine-Sottas syndrome type B (DSSB) are caused by missense or frameshift mutations of myelin protein zero (MPZ) gene. We identified an apparently silent synonymous c.411C>T transition in MPZ exon 3 (p.Gly137Gly) which segregated with DSS in a two-generation pedigree. Retro-transcriptional analysis of MPZ in the proband's archive sural nerve biopsy identified an r.410_448del mutant transcript which resulted from an activated cryptic splice site in exon 3 and led to an in-frame partial deletion of exon 3 (p.Gly137_Lys149del). Quantitative real-time polymerase chain reaction (QRT-PCR) compared with two unrelated CMT1B nerves carrying a frameshift c.306delA mutation (p.Asp104ThrfsX13) indicated that the r.410_448del was stable differing from the p.Asp104ThrfsX13-associated transcript which was subjected to nonsense-mediated decay. The report highlighted the possible pathogenic role of synonymous MPZ mutations and difficulties in interpreting results from routine mutational screenings., (© 2011 Peripheral Nerve Society.)

The pathogenesis of tomacula in mice with a null mutation of the myelin-associated glycoprotein (MAG) gene is not well understood. This study, using a novel teased nerve fiber technique, demonstrates that tomacula in MAG-deficient mice are formed by redundant myelin infoldings and outfoldings in the paranodal regions as early as 4 weeks after birth and increase in size and frequency with age. Although tomacula show degenerative changes with increasing age, there was no significant evidence of demyelination/remyelination. Longitudinal sections of normal teased nerve fibers show early redundant myelin foldings in externally normal paranodal regions. These data and the absence of internodal tomacula support a role for MAG in the maintenance of myelin at the paranodal regions.

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.

Soon after the description of Charcot-Marie-Tooth disease (CMT) in 1886, it became apparent that this syndrome is clinically and genetically heterogeneous. Neuropathological and electrophysiological studies have further dissected this syndrome into distinct categories that are now classified in a complex nosology of the inherited peripheral neuropathies. The recent advent of molecular genetics has dramatically increased our understanding of the underlying disease mechanisms. Genetic linkage studies have identified at least 17 genetic loci for different types of inherited neuropathies although most genes involved still remain to be found. The application of molecular genetics has already had an important impact on clinical practice and genetic counselling. Three genes responsible for hereditary motor and sensory neuropathy type I (HMSNI) or CMT1 have been identified: peripheral myelin protein 22 (PMP22) and myelin protein zero (MPZ) for the autosomal dominant form and connexin 32 (Cx32) for the X-linked dominant variant. The PMP22 gene is also involved in the majority of families with hereditary neuropathy with liability to pressure palsies (HNPP). The observation of a 1.5 Mb tandem duplication in chromosome 17p11.2, containing the PMP22 gene, in CMT1 and the reciprocal deletion in the same region in HNPP has provided a novel disease paradigm for autosomal dominant disorders, i.e. the gene dosage mechanism. The study of phenotype-genotype correlations in transgenic animal models for PMP22, MPZ and Cx32 mutations will help elucidate the underlying disease mechanisms and will provide a basis for gene therapy and/or other therapeutic approaches such as treatment with neurotrophic growth factors.

Fourteen patients with peripheral neuropathy and monoclonal IgG of undetermined significance are reported with a retrospective study of the clinical features, electrophysiologic and sural nerve biopsy findings. There were two groups. Five patients had a relapsing chronic sensorimotor polyneuropathy with clinical (5/5), electrophysiologic (4/5) and pathologic (5/5) features compatible with chronic inflammatory demyelinating polyneuropathies (CIDP). The nine others had a slowly progressive sensory (5/9) (SPNP) or sensorimotor (4/9) (SMPNP) axonal polyneuropathy. Four patients of the first group were treated with intravenous human immunoglobulin (400 mg/kg/day for five days) with significant clinical improvement. The motor conduction velocities and distal latencies of two of these patients improved following treatment, thus matching the clinical improvement. Our results on peripheral nerve biopsies confirm the differentiation of patients with CIDP from those with SMPNP and SPNP. There was no specific immunologic serologic reactivity in any of the cases.