ANCA-associated vasculitis with slowly progressive renal dysfunction: a little-known but treatable disease

The clinical spectrum of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) with renal involvement includes forms with a slowly progressive course. These forms are poorly recognised and, therefore, often associated with misdiagnosis and delayed treatment. We present here a case of slowly progressive AAV with renal involvement. A patient in her 50s with long-standing hypertension was evaluated for chronic renal impairment. Laboratory diagnostics revealed mild glomerular disease with relevant proteinuria and glomerular microhaematuria. Furthermore, significantly elevated ANCA of the antimyeloperoxidase (MPO-ANCA) type was detected. Renal biopsy provided evidence of arteriolosclerosis with an increased number of obliterated glomeruli but no evidence of active glomerulonephritis. The initiation of immunosuppressive therapy led to an improvement in both the clinical and the laboratory courses. Our case emphasises the importance of ANCA testing, particularly in cases of unclear glomerulopathy with an atypical presentation of ANCA-associated glomerulonephritis. It also illustrates the diagnostic challenges often encountered with slowly progressive AAV.