A 9-year-old boy is brought to emergency after a tonic-clonic seizure. He has a 3-week history of behavioral disturbance and a 2-week history of fever, fatigue, and a painful right knee. Cardiopulmonary examination shows no abnormalities. His laboratory studies are shown.
Hemoglobin 9.5 g/dL
Leukocytes 3,500/μL
Platelets 50,000/μL
Coombs test Positive
Urine protein +1
Urine blood +1
Which of the following is the most likely diagnosis?
