Review Question - QID 110013

A 47-year-old man presents to his primary care provider with difficulty swallowing. He reports a 5-month history of food getting stuck in his throat due to an inability to swallow. He has also felt more fatigued than usual. He has had to quit his swimming club due to tiredness. His past medical history is notable for hypertension, obesity, and a prior myocardial infarction. He takes enalapril, spironolactone, metoprolol, and hydrochlorothiazide. He has a 35-pack-year smoking history and occasionally drinks a glass of wine with dinner. His temperature is 99.1°F (37.3°C), blood pressure is 145/80 mmHg, pulse is 102/min, and respirations are 16/min. On exam, he is a tired-appearing man in no acute distress. No lymphadenopathy is noted. The patient is pale with concave nail beds on his fingers. An endoscopy is performed with results shown in Figure A. Which of the following additional findings is most strongly associated with this patient's condition?