For most myopathies, the weakening occurs primarily in the proximal muscles, the muscles close to the center of the body. These include the shoulder and upper arm muscles, and the thigh, pelvic and upper leg muscles. The distal muscles of the hands and feet may be involved in some cases and at more advanced stage of a disease. Individuals may initially feel fatigued doing only very light physical activity. Walking and climbing stairs may be difficult for many patients because of the involvement of the muscles in the pelvis and legs that are needed to stabilize the trunk.
Patients often find it difficult to get up out of a chair.
Muscles might be tight and stiff. A person may feel muscle pain, cramping, tenderness or aching feelings. As the muscle disease progresses, the muscles may atrophy, or shrink. When the muscles associated with breathing start to weaken, a person can develop significant breathing difficulties. For the inheritable myopathies, researchers are studying the DNA to try to locate the exact place where the defect occurs.