Hereditary motor and sensory neuropathy type 2C is genetically distinct from types 2B and 2D.

BACKGROUND Linkage analysis studies have identified 3 genetically different varieties of hereditary motor and sensory neuropathy type 2 (HMSN 2, also called Charcot-Marie-Tooth disease type 2, or CMT 2): HMSN 2A (linked to 1p35-p36), 2B (to 3q13-q22), and 2D (to 7p14). Hereditary motor and sensory neuropathy type 2C is characterized by diaphragmatic and vocal cord paresis; its disease locus has not been mapped. OBJECTIVE To determine whether the HMSN 2C phenotype, previously shown not to be linked to the HMSN 2A locus, is linked to the HMSN 2B or HMSN 2D loci. DESIGN Linkage analysis. SETTING AND PATIENTS Thirty-three subjects, including 12 affected individuals and 11 individuals at risk, in a large family with HMSN 2C. RESULTS Evidence was found against linkage of HMSN 2C phenotype to either the HMSN 2B or the 2D loci. CONCLUSIONS HMSN 2C is genetically distinct from HMSN 2A, 2B, and 2D. We think that at least 4 genetically distinct varieties of autosomal dominant HMSN 2 exist.