Two Sisters Producing Anti-U1RNP Exhibit Serological Concordance and Clinical Discordance

Abstract

Two sisters had autoimmune responses to the U₁RNP particle that were quantitatively similar and/or identical in molecular characteristics. No other autoantibodies were demonstrable. Both sisters immunoprecipitated only U₁RNA, had a reaction of identity in gel diffusion, bound the 68-kDa band in HeLa cell extract in Western blot, and reacted almost equally to a rabbit anti-idiotypic reagent made against either sister's isolated anti-U₁RNP Fab fragments. They both carried a DR₄ allele, which has been associated with anti-U₁RNP production in several studies. While the sisters both had Raynaud's phenomenon, their clinical pictures were otherwise dissimilar. One had a seizure disorder (Ju); the other had polymyositis and features of scleroderma (Je). In sister Ju, Raynaud's phenomenon was manifest for the first time in association with the appearance of precipitating anti-U₁RNP.

Keywords

Sisters Anti-U 1RNP Autoimmunity Polymyositis SLE Overlap syndromes

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