From presumed infection to systemic vasculitis: de novo granulomatosis with polyangiitis in pregnancy - a case report.

Granulomatosis with polyangiitis (GPA) is a rare ANCA-associated vasculitis. De novo presentation during pregnancy is exceptionally rare and may mimic severe infection, delaying diagnosis. This report concerns a case of new-onset GPA in a 26-year-old primigravid woman presenting in the second trimester with progressive refractory sinonasal disease initially treated as severe bacterial sinusitis. Despite repeated antimicrobial therapy and multiple ENT interventions, her condition deteriorated with development of hemoptysis and cavitating pulmonary lesions. Histopathology demonstrated necrotizing granulomatous inflammation, and further evaluation revealed ANCA positivity with anti-PR3 antibodies, confirming GPA at approximately 22 weeks of gestation. Management was complicated by rapidly progressive multisystem disease, concern for evolving renal involvement, opportunistic pulmonary infection with Pneumocystis jirovecii, and the limited availability of pregnancy-compatible immunosuppressive therapy before fetal viability. Disease control was achieved with corticosteroids, intravenous immunoglobulin, azathioprine, and multidisciplinary reassessment, while rituximab was deferred until the postpartum period. Pregnancy was continued to 35 + 5 weeks of gestation, resulting in delivery of a live female neonate appropriate for gestational age. At 2-year follow-up, maternal remission was sustained and the child remained clinically well. This case highlights the diagnostic challenges of de novo GPA during pregnancy and demonstrates that favorable maternal and neonatal outcomes remain possible with timely multidisciplinary management.