Tubular nephropathy in chronic polyarthritis

Disc electrophoresis and N-acetyl-beta-D-glucosaminidase (NAG) of urine are sensitive indicators of renal damage. In 28 from 50 patients with definite rheumatoid arthritis, a tubular proteinuria and a high urinary NAG-excretion and in 10 other patients one of these pathological parameters were detected. A positive correlation with disease activity was noted. Both methods are able to demonstrate a rheumatoid involvement of renal function.