Alternatively sized duplication in Charcot- Marie- Tooth disease type 1A

Motor and Sensory Neuropathy type 1) is the most common hereditary peripheral neuropathy. The main characteristics are hollow feet, distal muscle atrophy and weakness, decreased nerve conduction velocities and nerve biopsies showing signs of extensive de- and remyelination (1, 2). CMT1 is genetically heterogeneous, with linkage to at least three dominant loci. The most frequent form, CMT1A, is linked to chromosome 17pll.2 (3, 4). A minority of patients show linkage to chromosome lq (CMT1B) (5-8) or chromosome X (9, 10). In the majority of CMT1A cases a 1.5 Mb DNA duplication is present on chromosome 17pl 1.2 which segregates with the disease (11, 12). Altered gene dose is considered to be the mechanism for CMT1A. This hypothesis was supported by the identification of patients with signs of demyelinating neuropath