Atypical Kawasaki Disease in a 5-month-old Infant.

Kawasaki disease (KD) is an acute febrile vasculitis primarily affecting medium-sized arteries in children under 5 years. Infants under 6 months represent a diagnostic challenge due to atypical or incomplete presentations, increasing the risk of coronary artery lesions and complications such as aneurysms. Early diagnosis and treatment with intravenous immunoglobulin (IVIG) and aspirin are crucial to prevent long-term cardiac sequelae. We report a rare case of KD in a 5-month-old Bangladeshi girl presenting with prolonged fever, rash, and sterile pyuria. Initial evaluations pointed to partially treated meningitis, delaying KD diagnosis. Subsequent symptoms included edema, osteoarthritis, and persistent inflammation, leading to an echocardiographic detection of a small coronary aneurysm. Treatment with IVIG, aspirin, and corticosteroids resulted in the resolution of symptoms and normalization of cardiac findings. Infants below 6 months often present with incomplete KD, complicating diagnosis and delaying treatment. This case underscores the importance of considering KD in febrile infants with persistent inflammation, even in the absence of classic symptoms. Echocardiography and laboratory markers remain essential for early detection and management. Increased awareness and timely intervention in atypical and incomplete KD presentations are critical for reducing complications, particularly in high-risk groups like infants under 6 months.