children s health issues
Myotonia Congenita
Introduction
Myotonia congenita is an inherited disorder that causes muscle stiffness and muscle enlargement. It affects what most people think of as muscle, the type that can be contracted to move the various parts of the body. Myotonia refers to delayed relaxation after muscle contraction, which can cause muscle stiffness. Myotonia congenita has 2 main forms, Thomsen disease and Becker disease. Both of these forms are caused by defects in the same gene. Thomsen disease is Dominant disorders , which means a defective gene from only one affected parent is needed to pass the trait on to offspring. Symptoms of Thomsen disease usually start in infancy to 2 to 3 years of age. Becker disease is more common and is Recessive disorders , which means a defective gene from both parents is needed to pass on the trait. Symptoms of Becker disease start from 4 to 12 years of age, and it tends to be more severe than Thomsen disease. Myotonia congenita should not be confused with Congenital Myopathies , a separate disorder. 