The diagnosis and classification of polymyositis.

[inclusion body myositis]

Polymyositis is classified as a separate entity among idiopathic inflammatory myopathies but it is considered as the least common since it is an exclusion diagnosis . This myopathy usually presents with subacute-chronic symmetric proximal limb weakness , although some extramuscular manifestations are common . Creatine kinase values may be increased up to 50 -fold in active disease . Muscle biopsy is characterized by endomysial inflammatory infiltrate consisting predominantly of CD 8 + T cells that invade healthy muscle fibres expressing the MHC-I antigen . Although serum autoantibodies , EMG and imaging techniques can help in diagnosis , muscle histopathology is a pivotal value . The clinical picture together with the pathological findings confers the also called PM pattern . A broad differential diagnosis is needed before concluding a diagnosis of pure PM . Sporadic inclusion-body myositis , toxic , endocrine and metabolic myopathies as well as muscular dystrophies are the major categories to be ruled out . Finally , a diagnostic algorithm for suspected cases of PM is also proposed .

Diseases
Validation

Diseases presenting "muscle biopsy" symptom

cadasil

canavan disease

cohen syndrome

epidermolysis bullosa simplex

familial mediterranean fever

focal myositis

inclusion body myositis

neuralgic amyotrophy

pyomyositis

pyruvate dehydrogenase deficiency

sneddon syndrome

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