Autoantibodies in inflammatory myopathies

[The clinical spectrum of dermatomyositis]

Dermatomyositis is characterized by marked clinical heterogeneity. Many classification schemes are available, based on internal organ involvement, presence of circulating autoantibodies and additional symptoms characteristic for other connective tissue diseases. Viral infections and underlying malignancies are possible mechanisms to trigger this autoimmune disease. Intensive clinical investigations to detect such malignancies are therefore required. The prognosis of the individual patient depends on the involvement of internal organs and the characterization of circulating autoantibodies. There are patients with rapidly developing subsets of dermatomyositis and those with slowly progressive disease. Therefore treatment has to be adjusted for the disease severity. Sometimes high dosages of corticosteroids in combination with immunosuppressive agents or immunoglobulins are required.

Autoantibody testing

Recent advances in neuroimmunology have led to improvements in the pathogenesis, diagnosis, prognosis, and treatment of many neuromuscular disorders. The value of autoantibody testing is increasing steadily in neurologic practice. Not all antibodies have a high yield in diagnosis. In some disorders, such as generalized adult onset of myasthenia gravis, Lambert-Eaton myasthenic syndrome,Miller Fisher syndrome, and multifocal motor neuropathy,autoantibody tests provide accurate diagnosis and can be considered biologic markers of these disorders.

Inclusion body myositis: genetic factors, aberrant protein expression, and autoimmunity

Sporadic inclusion body myositis (s-IBM) is an inflammatory myopathy mainly affecting elderly individuals. It has a chronic progressive course leading to severe disability. Immunosuppressive treatment is in most instances ineffective. S-IBM is morphologically characterized by mononuclear cell infiltrates and vacuolated muscle fibers with pathologic accumulation of a large number of different proteins. Recent research has focused on the expression of various factors that may contribute to the inflammatory reaction and the typical inclusions. This review summarizes the new information on genetic factors, abnormal protein expression and inflammation, which provides a basis for linking the different typical morphologic features of s-IBM to a cascade of pathogenic events.