A 21-day-old infant with hemangioma was brought to the hospital with enlargement of the hemangioma of the left thigh and purple discoloration around umbilicus. This led to the diagnosis of Kasabach-Merrill syndrome. Initial treatment with corticosteroid failed. The patient underwent radiotherapy that led successfully to improvement of both hemangioma and thrombocytopenia. After 2 years of follow-up, the patient has experienced long-term complications, including atrophy and growth retardation of the irradiated leg.