A 21-year-old woman with no significant medical history presented with a complaint of dyspnea on exertion. She noticed increasing dyspnea when she walked up two flights of steps. She is a lifelong nonsmoker, with no recent travel, pets, street drug use, or HIV risk factors. She denied any recurrent infections, cough, fever, chills, or hemoptysis. She is not receiving treatment with any medications. Her surgical and family histories were negative. The patient was afebrile. Her vital signs were unremarkable, and her oxygen saturation was 99% while breathing room air. A physical examination revealed a well-developed, well-nourished woman in no distress with the following characteristics: the neck was supple without thyromegaly or elevated venous pressure; the chest was symmetrical without dullness to percussion; breath sounds were clear to auscultation; heart beat was regular without murmur; the abdomen was without lymphadenopathy; and the extremities exhibited no muscle weakness or edema.