Mucinous nodules on the skin overlying a rheumatoid arthritic joint.

A rare case of mucinous nodules on the skin overlying rheumatoid synovitis in a 79-year-old man is described. The patient had a five year history of RA. The patient had complained of arthralgia in the left elbow joint, and X-ray demonstrated narrowing of thejoint space along with bone destruction. He underwent an intraarticular injection of dexamethazone and lidocaine. Three weeks later, he noticed two dome-shaped nodules about 5 mm in size developing on the elbow. Histopathological examination demonstrated poorly defined mucinous nodules in the upper dermis. The mucinous material positively stained with alcian blue and colloid iron, and was metachromatic with toluidine blue. These positive stainings disappeared after hyaluronidase digestion. Five to six weeks after being resected, both nodules recurred. Lesional injections of triamcinolone were effective. The intraarticular injections preceding the appearance of the nodules might have created channels from the joint space to the skin. Leakage of activated synovial cells, which produced hyaluronic acid, through the channels might have caused the mucinous stroma of the nodules.