Review Question - QID 212519

A 33-year-old woman presents to the emergency department with numbness and severe fatigue. She states that her symptoms started yesterday and have been gradually worsening. The patient is generally healthy, drinks alcohol on the weekends, and does not smoke. She was ill recently but recovered spontaneously. Her temperature is 102°F (38.9°C), blood pressure is 127/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for an anxious young woman who appears mildly confused. Neurological exam reveals she has decreased sensation to light touch bilaterally on her upper and lower extremities. Dermatologic exam reveals petechiae. Laboratory values are ordered as seen below.

Hemoglobin: 7.2 g/dL
Hematocrit: 25%
Leukocyte count: 6,500/mm^3 with normal differential

Serum:
Na+: 139 mEq/L
Cl-: 100 mEq/L
K+: 5.4 mEq/L
HCO3-: 22 mEq/L
BUN: 30 mg/dL
Glucose: 99 mg/dL
Creatinine: 1.9 mg/dL
Ca2+: 10.2 mg/dL

A peripheral smear is performed as seen in Figure A. Which of the following is the best treatment for this patient?