Myositis refers to muscle inflammation, often describing rare autoimmune diseases where the immune system attacks healthy muscle tissue, causing chronic inflammation, weakness, and pain. Inclusion Body Myositis (IBM) is a specific, progressive inflammatory myopathy that primarily affects muscles, leading to weakness and impaired function.
Understanding Inclusion Body Myositis
Inclusion Body Myositis is a rare, acquired muscle disorder involving inflammation and degeneration of muscle tissue. It often affects individuals over 50 and typically does not respond to standard immunosuppressive treatments, unlike other inflammatory myopathies.
IBM predominantly affects specific muscle groups, such as the quadriceps, forearm flexors, and hand muscles. A defining feature, which gives the condition its name, is the presence of “inclusion bodies” within muscle cells. These are abnormal protein aggregates found as intranuclear and intracytoplasmic vacuoles during microscopic examination.
Recognizing the Signs
Symptoms of Inclusion Body Myositis typically begin slowly and progress insidiously. Muscle weakness is a primary symptom, often starting in the quadriceps, leading to frequent falls, difficulty climbing stairs, or trouble getting up from a chair. Weakness in the forearm flexor muscles is also characteristic, making tasks requiring grip strength challenging.
Muscle atrophy, or visible shrinking, often accompanies the weakness, particularly in the forearms and thighs. Dysphagia, or difficulty swallowing, affects 30% to 50% of individuals with IBM. This can lead to choking, food getting stuck, or aspiration, where food or liquid enters the lungs, potentially causing pneumonia. The progression of muscle weakness also impacts balance and gait, increasing the risk of falls.
Diagnosis and Underlying Causes
Diagnosing Inclusion Body Myositis involves a comprehensive approach, starting with a clinical evaluation of muscle weakness patterns. Blood tests may show mildly elevated creatine kinase (CK) levels, but typical autoantibodies seen in other inflammatory myopathies are generally absent.
Electromyography (EMG) and nerve conduction studies identify muscle disease and rule out nerve issues. A muscle biopsy is the definitive diagnostic tool, where pathologists look for inflammatory cells, rimmed vacuoles, and abnormal protein aggregates. The exact cause of IBM remains unknown, though theories suggest a combination of age-related degenerative processes, autoimmune factors, and genetic predispositions. IBM is not considered a purely genetic or purely autoimmune disease.
Managing Inclusion Body Myositis
There is currently no cure for Inclusion Body Myositis, and it typically does not respond well to corticosteroids or other immunosuppressive drugs. Management focuses on symptom control and supportive care to maintain function and improve quality of life.
Physical therapy helps maintain muscle strength and flexibility, improve balance, and prevent contractures. Gentle, regular exercise is encouraged to preserve muscle function. Occupational therapy helps individuals adapt to daily activities and maintain independence, often using adaptive equipment.
For swallowing difficulties, strategies include dietary modifications, specific swallowing exercises, and speech therapy. In severe cases, feeding tubes or surgical interventions like cricopharyngeal myotomy may be considered to prevent aspiration. Fall prevention is also a significant aspect of management, often involving assistive devices and home modifications. Research efforts are underway to identify effective treatments.