beta 2-Microglobulin and systemic lupus erythematosus.

Serum beta 2-microglobulin (beta 2-M) was measured in 115 patients with systemic lupus erythematosus (SLE) on 192 occasions. Raised beta 2-M was found in 16.4% of patients with only extrarenal manifestations of SLE, in 29.2% of patients with renal manifestation but an endogenous creatinine clearance greater than 80 ml/min/1.73 m2 and in 65.7% of patients with decreased creatinine clearance. beta 2-M was higher in SLE than non-SLE glomerulonephritides matched for creatinine clearance. Using an arbitrary scoring system, renal, extrarenal and serological activity correlated with beta 2-M. Changes in clinical activity on repeat studies were reflected by changes in beta 2-M. Serum beta 2-M can serve as a monitor of disease activity in SLE.