Overlap syndromes with features of both PM and SSc are associated with PM-Scl and Ku antibodies. However, negative tests for these AABs do not exclude the possibility of PM-scleroderma overlap syndrome.
PM-Scl antibodies are directed against components of the exosome, a complex consisting of 11-16 proteins (20-110 kDa) located in the granular part of the nucleoli and in the nucleoplasm. The main targets of PM-Scl antibodies are proteins of 100 kDa (PM-Scl-100) and of 75 kDa (PM-Scl-75). PM-Scl antibodies are highly characteristic of, although not specific for, PM-scleroderma overlap syndrome . They are detectable in approximately 24% of patients with PM-scle-roderma overlap syndrome, in 8-12% with IIM, and in 1-16% with SSc. Apart from myositis, arthritis and Raynaud's phenomenon are the most common manifestations observed in PM-Scl antibody-positive patients. Cardiac and renal involvement is very rare. The prognosis for these patients is therefore relatively good. In childhood, the PM-Scl antibody-positive scleromyositis appears to be the most common scleroderma-like disease . The clinical course is relatively benign compared to that of juvenile dermatomyositis or scleroderma.
Ku antibodies are directed against DNA-binding, non-histone proteins (p70/ p80 heterodimers) and the catalytic subunit (p350) of DNA-dependent protein kinase (DNA-PK). Ku antibodies are detectable in patients with myositis-sclero-derma overlap syndrome but can also be found in patients with primary pulmonary hypertension, SLE, and other connective tissue diseases (reviewed in ).
Was this article helpful?
Did You Know That Herbs and Spices Have Been Used to Treat Rheumatoid Arthritis Successfully for Thousands of Years Do you suffer with rheumatoid arthritis Would you like to know which herbs and spices naturally reduce inflammation and pain 'Treating Rheumatoid Arthritis with Herbs, Spices and Roots' is a short report which shows you where to start.