Inclusion body myositis (IBM) is the most frequent acquired myopathy after age 45. It is distinguished from other inflammatory myopathies by its selective pattern of muscle involvement and slowly progressive course, and by the combination of inflammatory and degenerative muscle pathology and multi-protein deposits in muscle tissue. It typically presents with chronic insidious proximal leg and/or distal arm asymmetric muscle weakness leading to recurrent falls and loss of dexterity. Creatine kinase (CK) is elevated in IBM and needle electromyography (EMG) mostly shows a chronic irritative myopathy. Muscle histopathology demonstrates endomysial inflammatory exudates surrounding and invading non-necrotic muscle fibers often times accompanied by rimmed vacuoles and protein deposits. IBM is refractory to all known immunosuppressive therapies. It has been shown in small short-term trials that individualised exercise programs can lead to improvement or maintenance of muscle strength and aerobic capacity.
