Anti-Ribonuclear Protein (RNP)

The presence of anti-RNP antibodies in serum, in the context of positive antinuclear antibodies, and in conjunction with clinical findings and other laboratory tests, can aid in the diagnosis of Systemic Lupus Erythematosus (SLE) and Mixed Connective Tissue Disease (MCTD).  Antibodies to RNP antigen are found in an average of 25% of patients with Systemic Lupus Erythematosus (SLE), but can also be present in some other connective tissue diseases, such as Sjögren’s syndrome, systemic sclerosis and polymyositis. High titers of (isolated) anti-U1 RNP antibodies are highly characteristic for mixed connective tissue disease (MCTD). Antibodies to RNP are associated with a relatively benign disease course in SLE, with lower incidence of renal and central nervous system (CNS) disease.