Sustained remission of antineutrophil cytoplasmic antibody-mediated glomerulonephritis and nephrotic syndrome in mixed connective tissue disease

A woman diagnosed with mixed connective tissue disease (MCTD) developed an anti-myeloperoxidase (MPO) antineutrophil cytoplasmic antibody (ANCA) and nephrotic syndrome with normal serum creatinine. Percutaneous kidney biopsy showed pauci-immune glomerulonephritis with superimposed immune complex deposition. After treatment with cyclophophamide and prednisone, proteinuria decreased progressively to a level of 0.4 g/g creatinine, ANCA became undetectable, while serum creatinine remained normal seven years after the beginning of treatment. Sustained remission of nephrotic proteinuria with preserved renal function may follow treatment of ANCA-mediated disease developing in patients with MCTD.