From OMIM
Charcot-Marie-Tooth disease constitutes a clinically and genetically heterogeneous group of hereditary motor and sensory peripheral neuropathies. On the basis of electrophysiologic properties and histopathology, CMT has been divided into primary peripheral demyelinating (type 1) and primary peripheral axonal (type 2) neuropathies. The demyelinating neuropathies classified as CMT type 1, also known as HMSN I, are characterized by severely reduced motor nerve conduction velocities (NCV) (less than 38 m/s) and segmental demyelination and remyelination with onion bulb formations on nerve biopsy (see CMT1B; 118200). The axonal neuropathies classified as CMT type 2, also known as HMSN II, are characterized by normal or mildly reduced NCVs and chronic axonal degeneration and regeneration on nerve biopsy (see CMT2A1; 118210). Distal hereditary motor neuropathy (dHMN) (see 158590) is a spinal type of CMT characterized by exclusive motor involvement and sparing of sensory nerves (Pareyson, 1999). There are X-linked, autosomal dominant (see 118200), and autosomal recessive (see 214400) forms of CMT. The form of Charcot-Marie-Tooth neuropathy that maps to chromosome Xq13 (CMTX1) is X-linked dominant or X-linked intermediate; heterozygous females are more mildly affected than are hemizygous males. Genetic Heterogeneity of X-linked Charcot-Marie-Tooth Disease Ionasescu et al. (1991) presented data suggesting the existence of an X-linked recessive CMT disease on Xp22.2 (CMTX2; 302801). CMTX3 is caused by a genomic rearrangement between chromosomes 8q24.3 and Xq27.1. Cowchock syndrome (310490), which maps to chromosome Xq26, is also referred to as CMTX4. CMTX5 (311070) is caused by mutation in the PRPS1 gene (311850) on chromosome Xq22. CMTX6 (300905) is caused by mutation in the PDK3 gene (300906) on Xp22.  http://www.omim.org/entry/302800