A Prospective Natural History and Outcome Measure Discovery Study of Charcot-Marie-Tooth Disease, Type 4J

This is a multicenter, longitudinal, prospective observational natural history study of subjects with a molecularly confirmed diagnosis of CMT4J. The study will enroll 20 subjects of any age into a uniform protocol for follow-up and evaluations. The study will obtain demographic and medical history information. Natural history data will be collected prospectively on an annual basis and may include physical/neurological exams, standard laboratory tests, CMT outcome and disability measures, neuropsychological tests, nerve conduction studies (NCS), and imaging studies (muscle MRI). Pulmonary function test (PFT) and scoliosis series x-ray Subject visits will occur every 12 months + 4 weeks for up to 2 years. Subjects who terminate from the study prior to Visit 3 will undergo an early termination/end of study visit (EOS) if possible. The early termination/end of study visit is comprised of the Visit 3 assessments. If needed, the Investigator may conduct unscheduled visits with Sponsor's approval. No investigational product will be used during the study.