Thirty-three subjects in a large family with hereditary motor and sensory neuropathy (HMSN) type 2C were examined by linkage analysis at the Mayo Clinic, Rochester, MN. The HMSN 2C phenotype, including 12 affected and 11 at risk, were not linked to either the HMSN 2B or 2D loci. HMSN 2C is genetically distinct from HMSN 2A, 2B, and 2D. 
COMMENT. HMSN type 2C is a clinical variety of HMSN 2 manifested by motor and sensory neuropathy of the limbs and progressive weakness of the vocal cords, diaphragm, and intercostal muscles. HMSN 2 shows genetic heterogeneity, and at least 4 genetic varieties have ben confirmed: HMSN 2A (1p35-p36), HMSN 2B (3ql3-q22), HMSN 2D (7pl4), and HMSN 2C (not linked to any of these loci).
The many faces of Charcot-Marie-Tooth disease (HMSN) are reviewed in an editorial . Phenotype classifications in CMT include CMT1 (autosomal dominant, demyelinating), CMT2 (autosomal dominant, axonal presentation), CMT3 (autosomal recessive, axonal presentation), CMT4 (autosomal recessive, demyelinating presentation), and CMTX (X-linked, axonal, or demyelinating presentation). Both clinical and molecular classifications are discussed.
Neurotrophins and their relevance to neurologic disease are reviewed by Kernie SG, Parada LF (Arch Neurol May 2000;57:654-657). Neurotrophin therapy has potential in diseases of the peripheral nervous system especially because its function has been studied in peripheral sensory ganglia. Trials of subcutaneous injections of nerve growth factor (NGF), the prototypical neurotrophin, in diabetic polyneuropathy have shown promising results.