Dual-Positive Anti-Neutrophil Cytoplasmic Antibodies in Renal-Limited Vasculitis: A Case Report from Pakistan

The anti-neutrophil cytoplasmic antibodies (ANCAs) target different proteins of neutrophilic granules, mainly myeloperoxidase (MPO) and proteinase (PR3), and others.Dual-positive ANCA with both MPO and PR3 is an uncommon finding described in infections, autoimmune diseases, drugs, ANCA-associated vasculitis (AAV), COVID vaccination, and malignancies.An 18-year male patient presented with dyspnoea on exertion, weakness, and weight loss, without any systemic findings on examination.Baseline workup showed iron deficiency anaemia, proteinuria, and haematuria.After extensive investigations, serum ANCA was positive for both MPO and PR3, and the rest of the investigations, including bone marrow, radiological, autoimmune, biochemical, and microbial testing, were negative.He was treated as a case of AAV and started on steroids, which improved his symptoms.This case is an unusual presentation of dual-positive ANCA with renallimited vasculitis.High vigilance is required for early diagnosis of AAV in unusual presentations.