Acute hemorrhagic edema of infancy (AHEI) is a cutaneous leukocytoclastic vasculitis that affects children under 2 years of age and is clinically characterized by fever, extensive tender edema and large purpuric lesions that involve mainly the face, ears and limbs. AHEI typically exhibits an acute onset, with a short benign course followed by spontaneous and complete recovery. Visceral involvement is usually absent, and laboratory studies reveal no specific abnormalities. The pathogenic mechanisms underlying the development of AHEI remain unknown. We describe a patient with AHEI exhibiting transient renal involvement and hypocomplementemia. A 19-month-old Japanese boy was admitted to our hospital with a 2-day history of fever and purpura affecting his face, right ear and legs, and a 1-day history of painful edema of the right side of his face and his right lower leg. Laboratory studies revealed microscopic hematuria, proteinuria and hypocomplementemia affecting C4, C1q and CH50. A clinical diagnosis of AHEI was made, and the patient made a rapid and completely recovery without any specific therapy. We suggest that activation of the classical pathway of complement might be one of the pathogenic mechanisms underlying the development of AHEI.