Inclusion Criteria:

All patients must agree to take part in the study and sign a consent form. A teenager (age
13-17 years) considering enrolling must agree to take part in the study and sign an assent
form (depending on local ethics committee requirements).

Additional inclusion criteria are described below.

Inclusion Criteria: CMT1A Gene Modifier Study

Patients must have at least one of the following:

   1. Patient has a documented PMP22 duplication. AND/OR

   2. 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.

i. 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.

ii. 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.

Inclusion Criteria - Patients for CMT Exome Project

a. Patient has demonstrated neuropathy on nerve conduction studies or clinically diagnosed
genetic neuropathy, in the opinion of the investigator or genetic counsellor.

Inclusion Criteria - Controls for CMT Exome Project

   1. Person is a family member of a CMT patient who is enrolled in the CMT Exome Project.

   AND one of the following:

   2. Person does not have a peripheral neuropathy, in the opinion of the investigator or
   genetic counsellor.

   OR

   3. Person is suspected to have a peripheral neuropathy, but has not been examined at an
   INC site.

Exclusion Criteria

   1. Patient does not wish to participate or does not sign a consent form.

   2. For CMT Exome Project, patient has a genetically confirmed form of CMT (i.e. mutation
   in MFN2 causing CMT2A, mutation in GARS causing CMT2D, etc.).

   3. Patients with known neuropathy from a non-genetic source, such as chemotherapies (i.e.
   Vincristine, Taxol, Cisplatin), diabetes, alcoholism will be evaluated independently
   so that genetic contributions to their effects on CMT1A phenotypes can also be
   analyzed.