Clinical Reasoning: A 14-year-old with acute weakness, paresthesias, and headache.

A 14-year-old boy with a history of atrial tachycardia presented to the emergency department with acute right foot weakness. One month prior to presentation, he had a self-resolving diarrheal illness and bacterial pneumonia treated with antibiotics. Two weeks later, he endorsed a dull headache, increased irritability, and neck pain. One week prior to presentation, he developed intermittent urinary retention and episodes of flushing and redness of his right face. He fell 5 days prior to presentation and in the ensuing days, he complained of bilateral hip pain and paresthesias that progressively spread to involve bilateral thighs. On the day of presentation, the patient noticed weakness of his right ankle and foot. There was no history of fever. He denied joint pain, swelling, rash, or facial droop, but he did endorse mild sound sensitivity.