Congenital myopathy with type 2A muscle fiber uniformity and smallness.

ABSTRACT

We describe a 12-year-old girl with congenital myopathy. ATPase histochemical reactions and immunocytochemical analysis of muscle fiber-type composition with monoclonal antibodies against slow, fast (2A and 2B) and fetal myosin demonstrate that this congenital disease is characterized by type 2A muscle fiber uniformity and smallness. This is an unusual feature for a congenital myopathy in which the fiber type predominance, when present, is confined to type I.