Miyoshi myopathy
Overview
A rare genetic condition characterized by slow-progressing muscle weakness and atrophy that starts in the calves and progresses to the rest of the legs and arms. Occasionally the hips and shoulders may be affected but the heart and facial muscles are spared.
Symptoms
* Difficulty running * Tendency to fall * Leg muscle weakness * Leg muscle wasting * Difficulty walking on toes * Mild forearm wasting * Mild forearm weakness
Causes
Muscular dystrophy is caused by various genetic mechanisms. Duchenne’s and Becker’s muscular dystrophies are X-linked recessive disorders. Both result from defects in the gene coding for the muscle protein dystrophin; the gene has been mapped to the Xp21 locus. The incidence muscular dystrophy is about 1 in 651,450 persons in the United States. Duchenne’s and Becker’s muscular dystrophies affect males almost exclusively. Facioscapulohumeral dystrophy is an autosomal dominant disorder. Limb-girdle dystrophy is usually autosomal recessive. These two types affect both sexes about equally.
Prognosis
Prognosis of Miyoshi myopathy: bedridden in about 15 years
Treatment
No treatment stops the progressive muscle impairment of muscular dystrophy. However, orthopedic appliances, exercise, physical therapy, and surgery to correct contractures can help preserve the patient’s mobility and independence. Prednisone improves muscle strength in patients with Duchenne’s.