Genetics of Charcot Marie Tooth (CMT) - Modifiers of CMT1A, New Causes of CMT2

Inclusion Criteria: * Patients: o Must have demonstrated neuropathy on nerve conduction studies or a clinically diagnosed hereditary neuropathy, in the opinion of the site investigator. * Controls: * Must be a family member of a CMT patient who is enrolled in the 6602. * AND one of the following: * Does not have a peripheral neuropathy, in the opinion of the site investigator. * OR is suspected to have a peripheral neuropathy, but has not been examined at an INC site. CMT1A Modifier Study Inclusion Criteria: • Patient has a documented PMP22 duplication AND/OR • Patient has a first or second degree relative (parent, child, sibling, half-sibling, aunt, uncle, grandparent, grandchild, niece, or nephew) with a documented PMP22 duplication AND a clear link between that family member and the affected patient AND a phenotype consistent with CMT1A. * A clear link is necessary for a second-degree relative. For example, if a grandparent is affected and has a PMP22 duplication, and the parent does not have any signs, symptoms, or electrophysiology consistent with CMT1A, there is no clear link. * In cases where clear links are not available, genetic testing is required for the patient or the first degree family member who is not clearly affected. Exclusion Criteria * All Patients: Must not have known neuropathy from a non-genetic source, such as chemotherapies (i.e., Vincristine, Taxol, Cisplatin), diabetes, alcoholism. * CMT Exome Project Patients ONLY: Must not have a genetically confirmed form of CMT * All Participants: Does not wish to participate or does not sign a consent form.