pediatrics
Myotonia Congenita
Introduction
Myotonia congenita is an inherited disorder causing muscle stiffness and hypertrophy beginning during childhood. There are 2 main types with different modes of inheritance and manifestations. Diagnosis is by electromyography and sometimes muscle biopsy. Treatment is primarily supportive, but membrane-stabilizing medications may be of benefit. Myotonia refers to delayed relaxation after muscle contraction, which can cause muscle stiffness. There are 2 forms of myotonia congenita, Thomsen disease and Becker disease, both of which involve the same gene,CLCN1. Thomsen disease is Autosomal Dominant and manifests from infancy to 2 to 3 years of age. Becker disease is more common, is Myotonia congenita should not be confused with Congenital myotonic dystrophy , a separate disorder. 