PM/Scl antibodies target the PM/Scl exosome complex, and most reactivity is against 2 proteins, PM/Scl-75 and PM/Scl-100. They are present in 2% to 11% of SSc patients and are associated with SSc-myositis overlap syndrome and lcSSc. PM/Scl antibodies also occur in other autoimmune diseases such as polymyositis and dermatomyositis.
The presence of either PM/Scl-75 or PM/Scl-100 antibody is associated with calcinosis, and the co-occurrence of both antibodies is associated with inflammatory myositis.
However, each antibody may be associated with a distinct clinical phenotype; gastrointestinal symptoms and ILD are common in patients with PM/Scl-75 antibodies but less so in those with PM/Scl-100 antibodies. Internal organ involvement generally remains mild in patients with any PM/Scl antibodies, and the presence of these antibodies is associated with an overall favorable prognosis.
References:
Stochmal A, Czuwara J, Trojanowska M, et al. Antinuclear antibodies in systemic sclerosis: an update. Clin Rev Allergy Immunol. 2020;58(1):40-51. doi:10.1007/s12016-018-8718-8
Hamaguchi Y, Takehara K. Anti-nuclear autoantibodies in systemic sclerosis: news and perspectives. J Scleroderma Relat Disord. 2018;3(3):201-213. doi:10.1177/2397198318783930
D'Aoust J, Hudson M, Tatibouet S, et al. Clinical and serologic correlates of anti-PM/Scl antibodies in systemic sclerosis: a multicenter study of 763 patients. Arthritis Rheumatol. 2014;66(6):1608-1615. doi:10.1002/art.38428
Wodkowski M, Hudson M, Proudman S, et al. Clinical correlates of monospecific anti-PM75 and anti-PM100 antibodies in a tri-nation cohort of 1574 systemic sclerosis subjects. Autoimmunity. 2015;48(8):542-551. doi:10.3109/08916934.2015.1077231
PM/Scl-75
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