Anti-ribosomal P protein antibodies in a Japanese patient with systemic sclerosis

A 56-year-old Japanese woman developed Raynaud's phenomenon and digital ulcerations at the age of 50. She showed rapid and diffuse skin sclerosis; visceral involvement was mild. She showed no symptoms or laboratory findings suggestive of other collagen diseases, including systemic lupus erythematosus and Sjögren's syndrome. Based on the clinical and histological findings, she was diagnosed as having diffuse cutaneous systemic sclerosis (SSc). The patient's serum produced nucleolar and cytoplasmic staining by indirect immunofluorescence analyses on HEp-2 cell substrate and reacted with P0, P1 and P2 proteins in immunoblotting using purified ribosomal antigens. She was negative for anti-topoisomerase I, centromere, and U1RNP antibodies. Antiribosomal P protein antibodies are considered highly specific for systemic lupus erythematosus; this is the first case report of an SSc patient with anti-ribosomal P protein antibodies. The clinical features of SSc patients with these antibodies need to be clarified by an accumulation of cases.