Review Question - QID 214732

A 53-year-old woman presents to the clinic with swollen legs. Her legs feel "heavy" and "darker than they used to be." Her socks and shoes fit poorly and her hair is thinner. She denies shortness of breath, exertional fatigue, abdominal pain, changes in bowel habits, or rashes. She has a history of type 2 diabetes mellitus and Grave disease which has been definitively treated with a thyroidectomy. Her medications include metformin and levothyroxine. She works as a cashier, denies smoking and alcohol use, and has a remote history of intravenous drug use. Her temperature is 97.4°F (36.3°C), blood pressure is 118/71 mmHg, pulse is 77/min, and respirations are 16/min. On exam, her heart rate and rhythm are regular, and her lungs are clear to auscultation bilaterally. Her abdomen is soft without distention. She has bilateral lower extremity pitting edema up to her mid-calf with sparse hair, increased brown pigmentation, and scaling at the ankles. Which of the following is the most likely cause of this patient's symptoms?