Review Question - QID 109964

A 57-year-old woman presents to her primary care physician with weakness for the past 6 months with symptoms that have worsened recently. She feels fatigued, depressed, and has gained 10 pounds which she attributes to feeling too weak to go to the gym. She was recently treated for an ear infection with an antibiotic which she completed 3 weeks ago, and experienced a rash which she believes was an allergic reaction to her treatment. The patient has a medical history of diabetes mellitus that is well-controlled with insulin and metformin. She has been admitted multiple times for hypoglycemia secondary to missing meals. Her temperature is 99.5°F (37.5°C), blood pressure is 127/68 mmHg, pulse is 80/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for 2/5 strength in the patient's upper and lower extremities, sparse fine hair on her body, and a rash on her face and arms. Laboratory values are ordered as seen below.

Serum:
Na+: 139 mEq/L
K+: 3.3 mEq/L
Cl-: 100 mEq/L
HCO3-: 25 mEq/L
BUN: 20 mg/dL
Glucose: 70 mg/dL
Creatinine: 1.1 mg/dL
Ca2+: 10.2 mg/dL
AST: 12 U/L
ALT: 10 U/L

A muscle biopsy is obtained as seen in Figure A. Which of the following is the most likely explanation for this patient's presentation?