Rare copresent rheumatoid arthritis and gout: comparison with pure rheumatoid arthritis and a literature review.

Copresent rheumatoid arthritis (RA) and gout is seldom reported. This study summarizes the findings of eight cases of copresent RA and gout and compares them with 31 pure RA cases. Additional reported cases were retrieved from the current literature by Medline search. Patients with copresent RA and gout were older (p = 0.014) and predominantly male (p < 0.01). Synovial fluid, positive for urate crystals, was aspirated most frequently from the knee (five out of eight), followed by the first metatarsophalangeal joint (three out of eight). Serum creatinine and urate levels in the copresent group were significantly higher (p < 0.01, both), and serum hemoglobin was lower (p = 0.04) than those with pure RA. Copresent subjects had much lower percentage of positive rheumatoid factor (RF) tests than patients with pure RA (37.5 vs 80.6%). Only one copresent subject had both RF and anti-cyclic citrullinated peptide antibody. Of copresent subjects, 75% had gouty arthritis before diagnosis of RA, which is consistent with earlier reports. Seven copresent subjects had gout attacks under disease-modifying antirheumatic drug use. This study revealed that polyarthritis negative for RF in a previously gouty patient may be RA and vice versa. This combination occurs more frequently in males. Moreover, anti-CCP antibody examination is not helpful for this diagnosis. Therefore, physicians must obtain synovial fluid for analysis in joints with intense swelling, especially in old RA subjects with renal insufficiency or involvement of lower extremities. Conversely, RA must be considered in gouty patients with polyarticular involvement.