A Case of Crescentic Glomerulonephritis Complicated with Hypocomplementemic Urticarial Vasculitis Syndrome and ANCA-Associated Vasculitis

Systemic urticaria in a 64-year-old woman was diagnosed as leukocytoclastic vasculitis by a punch biopsy of the skin. Her physical findings improved after prescription of prednisolone at a dose of 20 mg/day, but the skin rash relapsed with renal dysfunction, proteinuria, and hematuria when the dose of prednisolone was reduced over a period of 9 months to 1 mg/day. She was admitted to our institute for further examination, when urinary protein and plasma creatinine levels were 0.8 g/day and 1.7 mg/dL, respectively. Complement analysis showed that levels of total hemolytic component, component C3 fraction, and component C4 fraction were 30∼60% of normal values and the titer of anti-neutrophil cytoplasmic antibody for myeloperoxidase (MPO-ANCA) was 89 EU (normal range, <10 EU), though there were no immunologic disorders such as systemic lupus erythematosus. Cellular crescentic glomerulonephritis was observed by light microscopy, and immunofluorescent studies showed positive staining for IgG, IgM, C3, C4, and C1q. Electron microscopy showed mesangial and subendothelial deposits with circumferential mesangial interposition. She fulfilled the diagnostic criteria for hypocomplementemic urticarial vasculitis syndrome (HUV), and ANCA-associated vasculitis (AAV) was also indicated by small vessel vasculitis and positive MPO-ANCA. Steroid pulse therapy with methylprednisolone followed by oral prednisolone improved her general condition and hypocomplementemia, and MPO-ANCA became negative. HUV and AAV are distinct clinical disorders, though both affect small blood vessels. Here we report a case of AAV-complicated HUV with crescentic glomerulonephritis.