Pseudohypertrophy of muscles of thenar eminence in X-linked muscular dystrophy (Becker type).

Introduction X-linked muscular dystrophy (MD) occurs in 2 forms, mild and severe. The severe type, first described by Duchenne in 1868, is characterized by presentation before the age of 6 years, rapid progression of muscle weakness, inability to walk by the age of 12 years and death before the age of 20 years. It was Becker and Kiener (1955) who first delineated a 'benign' form, in which the condition presents later and pursues a slower course. This is a distinct entity and not simply a part of a spectrum of severity. Whether or not the mild type should be further subdivided remains debatable (Shaw and Dreiffuss, 1969). In both forms, muscular pseudohypertrophy, especially of the calf muscles, is common. A case is now reported of Becker (mild type) MD in which pseudohypertrophy of the muscles of the thenar eminence was prominent.