Chapter 17

MYOPATHIES Clinical Features Myopathies are diseases that primarily affect the muscles and are usually characterized clinically by weakness, fatigue, or stiffness (myotonia). They are usually characterized by symmetrical proximal muscle weakness and wasting, normal sensation, and normal stretch reflexes. More than one-half of muscle bulk must be lost before functional weakness can be demonstrated on clinical examination. Achings or muscle cramps can be present. The patient's complaints usually localize the weakness to a certain group of muscles. The questions listed in Box 17-1 should be answered. The neuromuscular examination (see Chapter 5) should give the examiner a good idea of muscle groups affected, acuteness or chronicity of disease, progression of disease, and inheritance pattern in familial myopathies.