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Hereditary Motor Sensory Neuropathies (HMSNs): An Overview

Introduction

Hereditary Motor Sensory Neuropathy (HMSN) is a name given to a group of different neuropathies that are all characterized by their implications on both the afferent and efferent neural communication. HMSNs are characterized by atypical neural development and degradation of neural tissue. The two common forms of HMSNs are either hypertrophic demyelinated nerves or complete atrophy of neural tissue. Hypertrophic condition causes neural stiffness and a demyelination of nerves in the peripheral nervous system, whereas the complete atrophy of neural tissues causes the breakdown of axons and neural cell bodies. Patients affected with this pathophysiological condition experience progressive muscle atrophy and sensory neuropathy of the extremities. Originally, the term “hereditary motor and sensory neuropathy” was historically used to denote the more common form called Charcot-Marie-Tooth (CMT) Disease. With the identification of a wide number of genetically and phenotypically distinct forms of CMT, the term HMSN is now used to describe a larger number of medical conditions (see Table H-3).

TABLE H-3Hereditary Motor Sensory Neuropathies (HMSN): An Overview
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TABLE H-3 Hereditary Motor Sensory Neuropathies (HMSN): An Overview
Type Inheritance Eponym/Synonym Characteristics
HMSN I (classic CMT I) Autosomal dominant ☞Charcot-Marie-Tooth Disease

Onset during late childhood or adolescence

Variable degree of nerve hypertrophy

Myelin sheath degeneration

At least three subtypes (IA, IB, IC)
HMSN I variant Autosomal dominant ☞Roussy-Lévy Syndrome Combination of HMSN type I and Friedrich’s ataxia
HMSN II Autosomal dominant ☞Cowchock Syndrome Onset usually later than type I

Known as neuronal type

No nerve hypertrophy
HMSN III Autosomal recessive Dejerine-Sottas Syndrome Onset in infancy or childhood
Delayed motor development
Often severe nerve hypertrophy
HMSN IV Autosomal recessive ☞Refsum Syndrome Slow motor nerve conduction velocity
Retinitis pigmentosa
Cerebellar signs
HMSN V Mainly autosomal dominant (recessive forms exist) Strümpell-Lorrain Disease Neuropathy with spastic paraplegia with peroneal muscular atrophy and sensory loss
HMSN VI Mitochondrial DNA transmission (from mother only) ☞Leber Hereditary Optic Atrophy Neuropathy with optic atrophy
HMSN VII   Often included in Refsum Syndrome Neuropathy with retinitis pigmentosa
X-Linked HMSN X-Linked   Similar to HMSN I, but limited to males. Females can be mildly affected
HMSNL Autosomal recessive Hereditary Motor and Sensory Neuropathy-Lom Type

Peripheral neuropathy

Tendon areflexia

Sensory loss

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