Renal involvement in patients with polymyositis and dermatomyositis.

Renal involvement in patients with polymyositis (PM)/dermatomyositis (DM) is previously thought to be uncommon, but two main types of renal lesion have been described. First, acute tubular necrosis with renal failure related to myoglobulinemia and myoglobulinuria is a well-recognised feature of acute rhabdomyolysis. Second, chronic glomerulonephritis has been infrequently reported in a small group of patients with PM/DM. This study aims at investigating the incidence, severity and prognosis of renal disease in PM/DM patients, admitted to a single centre in a 10-year interval. The hospital records of 65 Taiwanese patients with PM/DM, examined between 1992 and 2002, were studied retrospectively. Of the 65 patients, 14 were found to have suffered varying degree of renal involvement, and the incidence rate was 21.5%. All the 14 patients had varying degree of haematuria and proteinuria. Acute tubular necrosis with renal failure developed in four patients with PM and in five patients with DM. Renal biopsy in two DM patients with overt proteinuria revealed IgA nephropathy in one and membranous nephropathy in the other. We, therefore, concluded that renal involvement in PM/DM patients is not as uncommon as previously thought.