PM/Scl-100

Laboratory assay overview

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular abnormalities, and cutaneous and visceral fibrosis. Some antibodies are considered highly specific for SSc, including Scl-70 (anti-topoisomerase 1) antibody, anti-centromere (CENP) antibodies, and anti-RNA polymerase III antibody and are classification criteria for disease defined by the American College of Rheumatology. Centromere antibodies are found in patients with a limited form of cutaneous systemic sclerosis, "CREST" syndrome, a complex of subcutaneous calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasias. RNA polymerase III antibodies target RNAP III epitopes 11 and 155. Antibodies to three major components of U1-snRNP (snRNP RNP A, U1-snRNP RNP C, U1-snRNP RNP-70kd): U1- are associated with scleroderma and inflammatory myopathy overlap syndromes. Anti-fibrillarin (anti-U3RNP) antibodies are associated with diffuse cutaneous SSc, frequent visceral involvement, and especially renal and cardiac involvement. In African-American patients, anti-fibrillarin antibodies are associated with severe pulmonary disease, pulmonary hypertension, severe small bowel involvement, and a poor prognosis. Anti-Th/To antibodies primarily bind to two proteins of the mitochondrial RNA processing (MRP) and the ribonuclease P complexes, are present in 1-13% of SSc patients, and are rarely found in other diseases. Anti-Th/To antibodies are primarily associated with localized cutaneous scleroderma, and associated with pericarditis, interstitial lung disease and a high frequency of “intrinsic pulmonary hypertension, and a poorer prognosis. Autoantibodies to PM/Scl, the human exosome complex, are found in polymyositis/scleroderma overlap syndromes. The majority of anti-PM/Scl reactivity is directed to one of two proteins: PM/Scl100 and/or PM-Scl75.