Clinical Reasoning: A 7-Year-Old Boy With Acute-Onset Altered Mental Status

A 7-year-old boy presented with acute-onset headache, vomiting, and confusion during summer. Two months previously, he developed right thigh pain, causing intermittent limping. Three days before admission, headache; 1 day later, experienced fatigue, nausea, vomiting. On the of presentation, symptoms included behavioral change (showered 15 times), unsteadiness, new palmoplantar rash. He lethargy was transferred to our facility. His father had a recent gastrointestinal illness, but there were no other sick contacts. There weight changes, fever, tick/animal exposure, or travel. Past medical history prior herpes simplex virus (HSV)–positive facial lesion (at 5 years old). The patient took medications, known allergies, developmentally normal, appropriately vaccinated. general examination, somnolent irritable, palpable mass palmar/solar petechiae. Neurologically, arousable light touch, followed only simple midline commands, answered yes/no orientation questions responded all naming “I don't know.” Cranial nerves intact. normal muscle bulk/tone at least 3/5 strength throughout, encephalopathy limited assessment. sensation touch stretch reflexes, neutral plantar responses, dysmetria. sat in bed independently refused stand walk.