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

Background: Linkage analysis studies have identified 3 generically differen t varieties of hereditary motor and sensory neuropathy type 2 (HMSN 2, also called Charcoth-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 paresi s; 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 loc i. Design: Linkage analysis. Setting and Patients: Thirty-three subjects, including 12 affected individu als 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 t hink that at least 4 genetically distinct varieties of autosomal dominant H MSN 2 exist.