[Inclusion body myositis--a rarely recognized disorder]

Inclusion body myositis is the most common disabling inflammatory myopathy in the elderly. It is more frequent in men and after the age of 50 years. Inflammatory and degenerative features coexist. There is a T-cell mediated autoimmunity driven by in situ clonally expanded cytotoxic CD8-positive T-cells invading non-necrotic muscle fibres expressing MHC-I antigen. The hallmarks of degeneration are the deposition of protein aggregates and the formation of vesicles. The course of the disease is slow and the diagnosis is usually set after several years. The muscle weakness and wasting is assymetric, affecting predominantly distal muscles of the upper extremity and proximal muscles of the legs. The signs and clinical course can be characteristic, but the diagnosis is established by muscle biopsy. There is currently no evidence based effective treatment for sIBM. Prednisone, azathioprine, methotrexate, cyclosporine and IFN-beta failed. Oxandrolon did not improve symptoms. Treatment with intravenous immunglobuline (IVIG) induced in some patients a transient improvement of swallowing and of muscle strenght, but the overall study results were negative. A T-cell depleting monoclonal antibody (alemtuzumab), in a small uncontrolled study slowed down disease progression for a six-month period. Repeated muscle biopsies showed the reduction of T-cells in the muscle and the suppression of some degeneration associated molecules. An effective therapeutic mean should act on both aspects of the pathomechanism, on the inflammatory and the degenerative processes as well.