A 21-month-old previously healthy girl presented to the emergency department initially with fever, rhinorrhea, and poor oral intake. She was subsequently discharged from the hospital on amoxicillin for treatment of acute otitis media but presented hours later on the same day with continued poor oral intake, decreased urine output, and lethargy. The patient was afebrile on examination without a focal source of infection or evidence of meningismus, but she was lethargic and minimally responsive to pain and had reduced strength in the upper and lower extremities. Initial laboratory analysis revealed leukocytosis with a neutrophil predominance and bandemia, hyponatremia, mild hyperkalemia, hyperglycemia, elevated transaminases, a mild metabolic acidosis, glucosuria, ketonuria, and hematuria. Follow-up tests, based on the history and results of the initial tests, were sent and led to a surprising diagnosis.