Rheumatoid nodules are subcutaneous nodules that have the characteristic histology of a central area of fibrinoid necrosis surrounded by a zone of palisades of elongated histiocytes and a peripheral layer of cellular connective tissue. They occur in about 20% to 35% of RA patients, who typically are RF-positive and have severe disease. They tend to occur on the extensor surface of the forearms, in the olecranon bursa, over joints, and over pressure points such as sacrum, occiput, and heel. They frequently develop and enlarge when the patient’s RA is active and may resolve when disease activity is controlled. Methotrexate therapy can rarely cause increased nodulosis in some RA patients, even when the disease is well controlled. Nodules caused by methotrexate tend to be multiple small nodules on the finger pads.
Rheumatoid arthritis, xanthoma, gout (tophi), SLE (rare), amyloidosis, rheumatic fever (rare), sarcoidosis, multicentric reticulohistiocytosis, leprosy should be considered in a patient with subcutaneous nodules and arthritis.
Granuloma annulare lesions have been called “benign” rheumatoid nodules. Patients with granuloma annulare do not have arthritis and are RF-negative. These lesions are more common in childhood.