Clinical characteristics of patients with vasculitis positive for anti-neutrophil cytoplasmic antibody targeting both proteinase 3 and myeloperoxidase: a retrospective study

Anti-neutrophil cytoplasmic antibody (ANCA) may target proteinase 3 (PR3) or myeloperoxidase (MPO). Although a few patients with vasculitis have both MPO- and PR3-ANCA, the details of their clinical characteristics are not known. The objective of this study was to analyze the characteristics of patients with dual MPO- and PR3-ANCA-positive vasculitis. The medical records of patients with ANCA and vasculitis confirmed by biopsy were reviewed. The age at diagnosis, sex, and data on organ involvement of the kidney, lung, upper airways, skin, nervous system, and gastrointestinal tract were collected. Clinical variables were analyzed according to ANCA specificity. Of 85 patients with ANCA and vasculitis included in this study, 67 (78.8%) had MPO-ANCA, 10 (11.8%) had PR3-ANCA, and 8 (9.4%) had both MPO- and PR3-ANCA. Patients with MPO- PR3 + ANCA-associated vasculitis (AAV) were younger at diagnosis (median, 54.4 years; p < 0.05) than patients with MPO + PR3- AAV (67.0 years) or dual-ANCA AAV (MPO + PR3 + , 68.5 years). The initial glomerular filtration rate in patients with MPO + PR3- AAV (22.0 ml/min) was significantly lower than that in patients with MPO- PR3 + AAV (108.6 ml/min, p < 0.05), but was not different from that in dual-ANCA AAV patients (16.5 ml/min). Upper airway involvement also differed with ANCA type (MPO+ PR3- , 35.8% vs. MPO- PR3 + , 70.0% vs. MPO + PR3+ , 75.0%, p < 0.05). The involvement of other organs did not differ according to ANCA type. Age at diagnosis, kidney involvement, and upper airway involvement were associated with ANCA type. Patients with dual-ANCA-positive vasculitis had considerably more kidney dysfunction than patients with MPO- PR3+ AAV. They also had more upper airway involvement than patients with MPO+ PR3- AAV.