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

This project includes two projects. One is looking for new genes that cause Charcot Marie Tooth disease (CMT). The other is looking for genes that do not cause CMT, but may modify the symptoms a person has.

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.