What is the significance of antibodies to ribonuclear protein (RNP)?
Antibodies to RNP produce a speckled pattern on immunofluorescent ANA, reflective of the focal distribution of their target; the spliceosomal snRNPs in the nucleus are involved in pre-mRNA splicing. These antibodies are seen in a number of autoimmune diseases, including SLE, systemic sclerosis, and MCTD. The presence of very high levels of anti-RNP is highly suggestive of MCTD, a syndrome of overlapping disease manifestations with features of systemic sclerosis, SLE, and polymyositis. Patients with anti-RNP antibodies are more likely to have Raynaud’s syndrome, pulmonary hypertension, myositis, and esophageal dysmotility.