This form of nemaline myopathy usually becomes apparent between 10-20 years of age and accounts for approximately 13 percent of cases. The development of early motor skills is usually unaffected. Sometime during the late teens or early twenties, affected individuals develop slowly progressive muscle weakness.

Where does nemaline myopathy occur?

People with nemaline myopathy have muscle weakness (myopathy) throughout the body, but it is typically most severe in the muscles of the face; neck; trunk; and other muscles close to the center of the body (proximal muscles), such as those of the upper arms and legs.

How does myopathy start?

Myopathy refers to a disease of the muscles. In these cases, the muscles work less effectively than they should. That can occur when the muscles do not develop properly, when they have become damaged, or when they are lacking important components. Muscles normally work by contracting, which means becoming shorter.