Objective: To investigate the diagnosis and treatment of mixed connective tissue disease (MCTD) and myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) associated vasculitis, which is a rare clinical entity in medical practice.
Methods: A 35-year-old female of Asian origin was admitted to our hospital due to complaints of Raynaud's phenomenon, myalgia, arthralgia and fatigue. The patient was diagnosed as MCTD in the out-patient department 8 months prior to admission based on Alarcon-Segovia classification criteria of Raynaud's phenomenon, myalgia, arthralgia and a high anti-U1 ribonucleoprotein antibody level. Interstitial lung disease was determined by chest computed tomography. Renal biopsy was performed because of marked proteinuria on 24 h urine collection. Histopathological examination revealed glomerulonephritis with fibrocellular/cellular crescents, in which moderate staining of IgM was shown by direct immunofluorescence. She was tested positive for myeloperoxidase antineutrophil cytoplasmic antibody.
Results: High dose of methylprednisolone (500 mg/d for 3 days) was started intravenously when the results of renal biopsy were obtained. Oral prednisone and intravenous cyclophosphamide therapy (0.8 g/month) were continued for 12 months. Daily urinary protein loss decreased dramatically and serum creatinine was maintained at a normal level.
Conclusion: Corticosteroids and cyclophosphamide are effective in the treatment of MPO-ANCA associated glomerulonephritis in MCTD.