Hereditary motor and sensory neuropathy Type I (HMSN1) is also known as Charcot-Marie-Tooth disease (CMT1). It is characterized by demyelination and markedly reduced nerve conduction velocities. It is typically inherited as an autosomal dominant trait but can also be inherited as an X-linked or an autosomal recessive inheritance. The disease is characterized by upper and lower distal limb muscle weakness and wasting, impaired reflexes, foot deformity, and distal sensory loss. HMSN1 cannot be differentiated from HMSN Type II (HMSN2) on the basis of clinical features alone, although some signs occur more frequently in Type I. However, because HMSN1 involves demyelination and therefore slowed conduction velocities, accurate diagnosis can typically be made through nerve conduction studies.