Myofibrillar myopathy

Myofibrillar myopathy refers to a group of disorders that are characterized by muscle weakness (myopathy) that worsens over time. Myofibrillar myopathy primarily affects the skeletal muscles, which are the muscles that the body uses for movement. In some cases, the heart (cardiac) muscle is also affected.

The signs and symptoms of myofibrillar myopathy vary widely among affected individuals. People with this disorder typically begin to develop myopathy in mid-adulthood. However, the features of this condition can appear anytime between infancy and late adulthood. Myopathy most often begins in the hands, forearms, feet, and lower legs (distal muscles), but some people first experience weakness in the muscles near the center of the body (proximal muscles). The weakness can spread to other muscles. 

Other signs and symptoms of myofibrillar myopathy can include muscle pain (myalgia) or weakness and loss of sensation in the limbs (peripheral neuropathy). Affected individuals may also have skeletal problems, which can include joint stiffness (contractures) and abnormal side-to-side curvature of the spine (scoliosis). Some people with myofibrillar myopathy develop clouding in the lenses of the eyes (cataracts).

Some people with myofibrillar myopathy develop cardiomyopathy, which is a weakening of the heart muscle. In some cases, cardiomyopathy is the first sign of the disorder.

In rare cases, the muscles used for speaking, swallowing, or breathing are affected in people with myofibrillar myopathy. When the muscles used for breathing are involved, affected individuals may experience extreme tiredness (fatigue), breathing difficulties, and, in severe cases, respiratory failure.