How are the inherited neuropathies classified?
Most neuropathies that are initially labeled as idiopathic, and for which a cause is ultimately found, are inherited.
As a group, they are probably underdiagnosed.
They may be classified according to the pattern of inheritance (e.g., autosomal dominant: CMT1A–D, CMT2A–E; autosomal recessive: CMT4A–C; X-linked: CMTX); the gene involved (e.g., PMP22 : CMT1A and HNPP; MPZ : CMT1B); the conduction velocity (e.g., demyelinating: CMT1A, CMT1B; axonal: CMT2; or with conduction velocities in the intermediate range: CMTX); or by the type of nerves involved (e.g., motor: HMN; sensory: HSN; autonomic: HAN; or combinations of all three: HMSN, HSAN). In addition, peripheral neuropathy forms part of several of the inherited ataxic syndromes (e.g., Friedreich’s ataxia, spinocerebellar ataxias 3, 4, 10, and 18, among others) and accompanies many of the complicated hereditary spastic paraplegias.
Finally, there are many inherited multisystem disorders that include peripheral neuropathy as part of the syndrome (e.g., Fabry’s disease, Tangier disease, acute intermittent porphyria, and some of the leukodystrophies).
The term hereditary motor and sensory neuropathy (HMSN) is broadly interchangeable with CMT.
