Positive RA33 antibody is correlated with rheumatoid arthritis (RA) but can been found falsely elevated in patients with other autoimmune diseases, such as systemic sclerosis, mixed connective tissue disease, and juvenile idiopathic arthritis. Also, lupus patients with RA33 positive antibodies tend to have more erosive disease than lupus patients who present with arthralgia and nonerosive joint manifestations.