Anti-RNP antibodies are characteristic of mixed connective tissue disease, in which features of lupus, scleroderma, and polymyositis overlap. They are also present in some patients with systemic lupus erythematosus.
This test is part of the autoimmune workup in patients with multisystem symptoms suggestive of connective tissue disease, particularly when features of multiple diseases coexist. Very high anti-RNP titers in the absence of other lupus-specific antibodies particularly support mixed connective tissue disease. Sample type is serum.