Chloride channel disorders (Q94763)

Mutations in chloride channels (CLCN1) cause myotonia congenita, a non-dystrophic muscle diseases. Both autosomal dominant (Thomsen disease) and recessive (Becker disease) types have been described. Myotonia usually begins in the first or second decade of life, with men more severely affected than women. Patients classically have a hypertrophic, muscular build and experience a characteristic improvement in myotonia with exercise (“warm-up”). Virtually all patients report stiffness, with muscle pain and fatigue affecting quality of life