[Renal manifestations in dermatomyositis and polymyositis]

Renal involvement is usually considered to be rare in dermatomyositis and polymyositis. The aim of this prospective study was to reevaluate the renal changes which may occur in these two conditions. Twenty patients, 12 with dermatomyositis and 8 with polymyositis of the adult type, were investigated to determine the incidence, the severity and course of renal disease. The 24 hour proteinuria was over 0.1 g in 14 cases and greater than 1 g/24 hours in 6 cases, including one patient with the nephrotic syndrome. Microscopic haematuria was noted in 3 cases and pyuria in 8 cases. Endogenous creatinine clearance was significantly decreased (p less than 0.001) in patients with dermatomyositis compared with a control group of subjects paired for age, sex, weight and serum creatinine concentration. Renal biopsy (5 cases) showed minimal glomerular lesions (2 cases), endocapillary proliferation and extramembranous glomerulonephritis (1 cases) and amyloid deposits (1 case). Although the proteinuria, haematuria and pyuria responded to steroid therapy (except in 1 case), the creatinine clearance remained decreased during the course of steroids.