Review Question - QID 213556

A 2-year-old girl is brought to the emergency room by her parents for seizure-like activity earlier today. Her mother describes that she was napping when both of her arms began to twitch and she started foaming at the mouth. She was unresponsive during this time and the episode lasted a total of 30 seconds. The mother denies any fever, pain, recent trauma, changes in feeding, or gastrointestinal changes in her daughter. She states her daughter has recently been lethargic and is currently receiving antibiotics for an ear infection. The patient was born vaginally at home via a midwife without any complications. A physical examination is unremarkable. Results of her laboratory studies are shown below.

Hemoglobin: 13 g/dL
Hematocrit: 38%
Leukocyte count: 7,600/mm^3 with normal differential
Platelet count: 170,000/mm^3

Serum:
Na+: 136 mEq/L
Cl-: 101 mEq/L
K+: 3.9 mEq/L
HCO3-: 20 mEq/L
BUN: 25 mg/dL
Glucose: 34 mg/dL
Creatinine: 0.8 mg/dL
Thyroid-stimulating hormone: 3.2 µU/mL
Ca2+: 9.3 mg/dL
AST: 183 U/L
ALT: 220 U/L

What is the most likely explanation for this patient’s symptoms?