Catastrophic Antiphospholipid Syndrome Following Treated Antineutrophilic Cytoplasmic Antibody (ANCA) Vasculitis: Unusual Case Presentation.

Antineutrophilic cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare autoimmune disorder that affects small blood vessels, leading to systemic symptoms and kidney damage due to the production of autoantibodies. A limited number of case reports have explored the potential link between AAV and antiphospholipid syndrome (APS). Catastrophic antiphospholipid syndrome (CAPS), a severe variant of APS, is associated with high mortality and poor prognosis. We present a case of AAV that initially achieved complete remission, only to later develop CAPS. The presence of antiphospholipid antibodies at baseline may increase the risk of CAPS and thrombotic events in AAV patients. A high level of suspicion for this association, along with early detection of these antibodies, could facilitate prompt diagnosis and enable early, appropriate treatment, potentially improving the patient's outcome.