46-year-old man presents to the emergency department with a 5-day history of progressively worsening breathlessness on exertion and mild, general flulike symptoms. He also complains about night sweats and an intermittent low-grade fever, both of which started about 2 weeks ago.

On physical examination, the patient does not appear to be in any acute distress. His vitals signs are measured as a pulse of 89 bpm, blood pressure of 140/85 mm Hg, and a respiratory rate of 19 breaths/min. He is afebrile, with a temperature of 99.8°F (37.7°C). The chest examination reveals nothing out of the ordinary, and his cardiovascular and respiratory examinations, including auscultation, are unremarkable. The abdominal examination reveals no fluid thrill, shifting dullness, or bruit. The liver and the spleen are not enlarged. There are no palpable lymph nodes. Of note, there are multiple areas of hyperpigmentation, but otherwise the skin inspection is unremarkable; no hematomas, bruises, wounds, or scars are noted. ECG shows a sinus rhythm with a heart rate of 84 bpm, and the T waves are somewhat flattened in leads V1, aVL, and III, but they are otherwise unremarkable.