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

Inclusion Criteria:

Patient MUST be seen in person at one of the clinical sites involved in this study.

Charcot Marie Tooth disease type 1A (CMT1A) modifier gene study

   - Patient has a documented PMP22 duplication 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.

   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.

AND

   - Patient has agreed to take part in the study and has signed a consent form.

   - A teenager (ages 13-17) considering enrolling must agree to take part in the study and
   sign an assent form

Inclusion Criteria - CMT Exome Project

   1. Patient has demonstrated neuropathy on nerve conduction studies or a clinically
   diagnosed genetic neuropathy.

   2. Patient or first or second degree family member with a clear link as described in the
   CMT1A Inclusion Criteria part b has had negative MFN2 genetic testing, if has an
   axonal form of CMT (nerve conductions greater than 38 m/s) or negative testing for
   PMP22 duplication, deletion, sequencing, MPZ, and GJB1 if a demyelinating form of CMT
   is present (<38 m/s).

   3. More than one family member is willing eligible to participate.

i. Sample pedigrees showing optimal degrees of relationship are shown below. ii.
Participation includes being able to complete all aspects of the study, including the
giving informed consent, having a brief physical examination, and providing a DNA sample.

d. Patient has agreed to take part in the study and has signed a consent form. e. A
teenager (ages 13-17) considering enrolling must agree to take part in the study and sign
an assent form.

Inclusion Criteria - Controls

   1. Person does not have a peripheral neuropathy, as determined by the investigator.

   2. Person has understood the study and signed an IRB approved consent form. Teenagers
   (age 13-17 years) must sign an assent form.

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. 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.