Fever and Purpuric Lesions in a Preschool Child

A three-year-old previously healthy girl presented to an emergency department with erythematous lesions on her nose, both cheeks and left calf associated with fever and irritability. Her guardian reported that the child’s demeanour had changed from being pleasant and happy to general irritability approximately three weeks previously. Five days before presentation, she developed clear rhinorrhea and fever, but there was no cough, otalgia or headache. The child was reluctant to walk because of left leg pain. There was no history of travel or animal exposure. Her immunizations were current. On examination she was febrile (39.6°C), tachycardic (160 beats/min) and looked miserable. The chest was clear. A vibratory systolic ejection murmur was heard at the left sternal border without radiation and heart sounds were normal. There was no lymphadenopathy. The abdomen was soft and nontender with no organomegaly. A large, warm, tender, macular erythematous lesion was seen on the right face (Figure 1) with a central purplish bulla. The lesion on the tip of the nose consisted of a purplish-blue ulcer surrounded by erythema. A similar lesion was seen on the calf. The lesions were not indurated. The neck was supple. Figure 1) Lesions on the right side of the face and nose in a three-year-old girl with irritability, fever and pancytopenia. A pen marking placed by the care team outlines the border of the erythema anteriorly The white blood cell count was 0.5×109/L, with 3% neutrophils, 1% blast forms and 96% lymphocytes. The hemoglobin was 84 g/L and the platelet count 87×109/L. Blood cultures were done and empirical broad-spectrum antimicrobial therapy (ticarcillin/clavulanate, tobramycin and vancomycin) begun. A bone marrow biopsy and computed tomography scan of the neck were performed. The lesion on the right cheek, which opened spontaneously on day 2, was swabbed and cultures were taken. What is the diagnosis?