Myopathy is a skeletal muscle disease or neuromuscular disorder. Myopathy can be obtained or inherited, and can arise at birth or later in life. Myopathies can cause from endocrine disorders, metabolic disorders, muscle infection or inflammation, drugs, and mutations in genes. In several cases, myopathies can be caused by a malfunctioning gland (or glands), which produces either too much or too little of the chemical messengers called hormones. Some of these disorders, such as polymyositis, dermatomyositis and inclusion body myositis, develop when the immune system attacks muscles.
This inflammation damages muscle tissue and makes them weak. Patients with myopathy grow weakness in the large muscles around the neck, shoulders and hips. This causes argument in climbing stairs, getting up from a chair or toilet seat, or reaching for objects overhead. Most patients have little if any pain in their muscles, which distinguishes them from patients with other forms of muscle disease, from those who have joint pain due to arthritis, and from those with numbness or tingling in their hands and feet due to neurological problems. Polymyositis is an inflammation of the muscle tissue that leads to weakness.
Other symptoms of myopathy can involve muscle cramps, stiffness, and spasm. There are several different types of myopathies, some of which are inherited, some inflammatory, and some caused by endocrine problems. Genetic myopathies involve central core illness, centronuclear (myotubular) myopathy, myotonia congenita, nemaline myopathy, paramyotonia congenita, periodic paralysis and mitochondrial myopathies. These forms vary by symptoms, severity and genetic mutation. Certain form of centronuclear myopathy, also known as myotubular myopathy, have been found to be X-linked and primarily affects males.
Congenital myopathies are a heterogeneous group of disorders that cause hypotonia in infancy or weakness and delayed motor milestones later in childhood. Metabolic myopathies are characterized by the absence of a substance that is essential for normal muscle function and are related with genetic defects. Treatment depends on the cause, and goals are to slow progression of the disease and relieve symptoms. Physical therapy and exercise are important in the treatment of myopathy. Calcium supplements and antidepressants may be prescribed to counteract the side effects.