Silent renal involvement in systemic lupus erythematosus.

20 patients with active SLE without clinical evidence of renal involvement underwent percutaneous renal biopsy. 12 had varying proliferative changes on light microscopy. Of 19 ultrastructural examinations performed only 3 had no electron-dense deposits. Serum C3 and C4 levels were 63 +/- 8 and 8 +/- 2 mg% in patients with subendothelial deposits, compared to 142 +/- 27 and 27 +/- 6 mg%, respectively, in patients without deposits (p less than 0.01). All patients with diffuse proliferative changes had subendothelial deposits; however, one with normal light microscopy and another with focal proliferation also had them. It is concluded that no variant of lupus nephropathy can be excluded on clinical grounds alone.