Urinary excretion of beta 2-microglobulin predicts renal outcome in patients with idiopathic membranous nephropathy.

In patients with membranous nephropathy, treatment should be limited to those at risk for disease progression. Urinary beta 2-microglobulin excretion was measured in 30 patients with membranous nephropathy, a nephrotic syndrome, and normal renal function (endogenous creatinine clearance > 80 mL/min), who were subsequently monitored for a median of 48 months. Renal function deteriorated in 11 of the 14 patients with a beta 2-microglobulin excretion > 500 ng/min and in only 2 of the 16 patients with a beta 2-microglobulin excretion < or = 500 ng/min (P < 0.001). The measurement of urinary beta 2-microglobulin excretion thus contributes to the identification of patients with membranous nephropathy at high risk for developing renal insufficiency and may provide guidance for early immunosuppressive treatment.