Serum homocysteine and methylmalonic acid in patients with rheumatoid arthritis and cobalaminopenia.

To analyze the significance of cobalaminopenia (< 200 pmol/l) in patients with severe rheumatoid arthritis (RA).We studied 42 patients with RA and cobalaminopenia (incidence 4%). Most patients had severe and longstanding disease. Concentrations of homocysteine, methylmalonic acid (MMA), gastrin, and pepsinogen 1 were analyzed in sera that had been stored frozen. A capillary gas chromatographic mass spectrometric technique was used to determine homocysteine and MMA.As a group, patients had significantly higher levels of serum homocysteine and serum MMA than laboratory reference probands (p < 0.0001 and p < 0.005, respectively). Individually, 20 of 39 patients had elevated serum levels of homocysteine (> 15 micromol/l). In 12 of 39 patients serum levels of MMA were elevated (> 0.37 micromol/l). Twenty of 42 patients had biochemical signs of disturbed gastric function.Our findings were compatible with the hypothesis that cobalaminopenia is one of several biochemical signs of gastrointestinal dysfunction in patients with severe RA. It is suggested that the hyperhomocysteinemia associated with vitamin B12 deficiency, folate deficiency, vitamin B6 deficiency, and impaired renal function may have a role in promoting high cardiovascular morbidity in patients with RA.