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.