INTRODUCTION

The rheumatoid nodule is the most common cutaneous manifestation of rheumatoid arthritis (RA) [1,2]. Although nodules commonly are found on pressure points (such as the olecranon process), they may occur at other sites, including ones within internal organs of the body. Thus, bedridden patients can develop nodules on the occiput and ischial areas, and nodules occasionally form on the Achilles tendon and vocal cords [3]. Rheumatoid "nodulosis" is characterized by multiple nodules on the hands and multiple subchondral bone cysts known as "geodes" [4]. These nodules tend to occur on extensor surfaces adjacent to joints, elbows, and fingers, as well as the forearm, metacarpophalangeal and proximal interphalangeal joints, occiput, back, heel, and other areas [5].

The clinical and histopathologic features, diagnosis, and treatment of rheumatoid nodules will be reviewed here. The articular features and an overview of the systemic and nonarticular manifestations of RA are presented separately. (See "Clinical features of rheumatoid arthritis" and "Overview of the systemic and nonarticular manifestations of rheumatoid arthritis".)

PREVALENCE AND CLINICAL SIGNIFICANCE

Subcutaneous nodules — Palpable nodules in the subcutaneous tissues have been reported at initial presentation in 7 percent of patients with RA [6] and are found at some time during the disease course in 30 to 40 percent of patients [7]. The vast majority of nodule formers have positive tests for rheumatoid factor [1]. Nodules are found in 75 percent of patients with RA-associated Felty’s syndrome [5]. RA patients with nodules are also more likely to develop vasculitis [8]. Limited data suggest that many patients with rheumatoid nodules have a positive test for antibodies to citrulline containing peptides (eg, anti-CCP) [9]. In general, patients with rheumatoid nodules tend to have a severe RA phenotype, with more rapid progression of joint destruction than other patients with RA [10]. Rheumatoid nodules have also been noted in occasional patients with systemic lupus erythematosus, ankylosing spondylitis, granuloma annulare, and chronic active hepatitis, and they have been associated with antiphospholipid antibodies in patients with RA, as well as in healthy children and adults [5].

The size of the nodules varies from 2 mm to 5 cm; they are firm, nontender, and moveable in subcutaneous tissue (picture 1) [5].

In many cases, the nodules are neither symptomatic nor a cosmetic concern. However, rheumatoid nodules can be painful and/or disfiguring, can interfere with function, and can cause compressive neuropathies. Some patients find the nodules more distressing than the arthritis. The nodules may also ulcerate and thus serve as a site for local infection or other distant infectious complications by hematogenous spread of bacteria.