Extreme thrombocytosis and ANCA-associated vasculitis in an adult patient: a case report

We describe the case of a 39-year-old woman who presented with extreme reactive thrombocytosis as a prominent and unusual feature in the context of anti-neutrophil cytoplasmic antibody (myeloperoxidase, MPO)-associated vasculitis. To our knowledge, this is the first reported case in an adult patient where marked thrombocytosis was part of the initial presentation of ANCA-associated vasculitis.

The patient presented with a two-month history of constitutional symptoms and polyarticular pain. Laboratory evaluation revealed extreme thrombocytosis, impaired renal function, and positive MPO-ANCA. Renal biopsy demonstrated rapidly progressive pauci-immune crescentic glomerulonephritis consistent with MPA. Based on these findings, a diagnosis of ANCA-associated vasculitis was established. Treatment with high-dose corticosteroids and intravenous cyclophosphamide led to clinical improvement, including resolution of thrombocytosis and recovery of renal function.

Although the clinical features of ANCA-associated vasculitis were typical, the presence of extreme thrombocytosis may indicate a heightened inflammatory response and deserves careful evaluation. Early recognition and prompt treatment are essential to prevent irreversible organ damage and other complications.