A 34-year-old white man with no history of respiratory ailments presents with gradual onset of shortness of breath and the feeling of being “winded” with vigorous walking. His dyspnea gradually progressed over the next several weeks to the point where climbing a single flight of stairs left him markedly short of breath.
He reports having previously been in good health, with the exception of dyslipidemia, a 17–pack-year history of smoking with cessation at age 29 years, gastroesophageal reflux disease, and prior appendectomy at age 26 years. The patient also complains of an intermittent, dry cough but no hemoptysis, fever, or chills. There is no history of muscle weakness, arthritis, or arthralgia, and no family history of lung disease or tuberculosis. He works as a computer programmer and project manager. There is no history of exposures to fumes, dusts, mold, silica, or asbestos, and he denies any drug use. He was initially evaluated by his primary care physician, who prescribed a short course of antibiotics for possible pneumonia, with no relief in symptoms, and was referred for ancillary testing as well as pulmonary consultation.