Seizure Disorders USMLE Step 1 Practice Question

A 3-year-old previously healthy boy is brought to the emergency department by his mother after experiencing a seizure at home. She reports that this morning he developed fever (39.5°C), rhinorrhea, and cough consistent with an upper respiratory infection. While playing, he suddenly became unresponsive, his body stiffened, and his limbs jerked rhythmically for approximately 45 seconds. After the seizure ended, he was drowsy but gradually returned to baseline mental status over 10 minutes. Vital signs now show temperature 39.2°C, heart rate 120/min, respiratory rate 22/min, and blood pressure 104/66 mmHg. On examination, he is alert and oriented, with normal neurologic findings. Laboratory studies show white blood cell count 11,500/µL, normal serum electrolytes, normal glucose, and normal calcium. Head CT is unremarkable. Which of the following is the most likely diagnosis?