Refractory Kawasaki Disease With a Coronary Artery Aneurysm in a Three-Month-Old Infant: Diagnostic Challenges and Rescue With Infliximab.

Kawasaki disease (KD) is an acute systemic vasculitis and the leading cause of acquired heart disease in children. Diagnosis is particularly challenging in early infancy due to incomplete presentations. We describe a three-month-old infant with persistent fever, irritability, and lymphadenopathy who was initially treated for bacterial infection. By Day 7, the patient developed conjunctivitis, cracked lips, and pharyngeal congestion, meeting criteria for incomplete Kawasaki disease. Laboratory findings included leukocytosis, anemia, thrombocytosis, elevated C-reactive protein, and hypoalbuminemia. Initial echocardiography was normal; intravenous immunoglobulin (2 g/kg) with aspirin led to temporary improvement. Fever recurred, and repeat imaging revealed a right coronary artery aneurysm. Despite additional immunoglobulin and corticosteroids, the patient improved only after infliximab, with regression of coronary changes. This report emphasizes the diagnostic challenges of incomplete KD in early infancy, demonstrates practical application of the 2017 American Heart Association (AHA) diagnostic algorithm, and highlights the role of timely escalation to biologic therapy in refractory cases.