Renal Complications of Dermatomyositis

Both DM or PM relatively rarely cause renal involvement [1]. To date, few reports have described renal manifestations in patients with either PM or DM [2–4]. Dyck et al. described five patients with biopsy-proven primary idiopathic PM, normal kidney function and 24 h urine protein excretions ranging from 2.1 to 4.1 g. Four of the five patients underwent a renal biopsy, and all four were found to have mesangial proliferative glomerulonephritis. Three of the four biopsies underwent immunofluorescent staining showing diffuse mesangial deposits of IgG and IgM, and rare IgA and C3 immunoreactants with the same distribution. Only one of the five patients had decreased C3 levels. Pasquali et al. [3] prospectively studied the renal manifestations of 12 patients with DM and eight with PM. Eleven of the 20 patients had a protein excretion rate of more than 500 mg/24 h. The two patients with DM were found to have minimal change disease and mesangial proliferative glomerulonephritis, while another three patients with PM were found to have minimal change disease, amy-loidosis, and membranoproliferative glomerulonephritis [3]. A recent retrospective study of 65 Taiwanese patients with PM/DM hospitalized between 1992 and 2002 has found a varying degree of renal involvement in 14 (21.5%) of them [4]. All the 14 patients had from mild to prominent hematuria and proteinuria, and in four patients with PM and in five patients with DM acute tubular necroses with renal failure were found. Renal biopsy in two DM patients with overt proteinuria revealed IgA nephropathy in one and membranous neph-ropathy in the other [4]. Corticosteroids, with or without other immunosuppressive agents, may ameliorate the glomerulonephritis [2, 3, 5]. In the study by Dyck et al. [2], four of the five patients were followed for 2–7 years after treatment, and none had a recurrence of their renal disease or of their PM, while two of the four patients were on maintenance steroids for approximately 4½ years. One patient, who was in remission within 3 months after the initiation of corticosteroid and methotrexate therapy, underwent a repeat renal biopsy 18 months latter, the results of which were normal. As demonstrated in the study by Dyck et al. [2], both the myositis and proteinuria improved in concert with corticosteroid therapy.

Isolated case reports have noted the presence of various glomerulopathies with PM [5, 6]. Recently, a 28-year-old male with PM and nephrotic-range proteinuria has been reported [7]. Muscle biopsy confirmed the diagnosis of PM, and a renal biopsy demonstrated IgM mesangial glomerulonephritis. Following a short-course of prednisone, both the myositis and proteinuria resolved.