-year-old man was referred to our institution for further evaluation of
slowly progressive dyspnea on exertion. His symptoms started 3 years
prior to presentation, and consisted of episodes of shortness of breath
related to exertion. He did not complain of cough, fever, hemoptysis,
wheeze, or chest pain. He was initially treated with several
antiasthmatic medications, including inhaled bronchodilators, inhaled
steroids, and theophylline, without any relief of symptoms.
Subsequently, the shortness of breath became progressively worse over
time. Due to lack of improvement with empiric therapy, a comprehensive
medical evaluation was performed by the primary physician. Findings on
initial testing revealed arterial hypoxemia on arterial blood gas
analysis, and a markedly reduced diffusing capacity on pulmonary
function testing. Chest radiography, ventilation/perfusion scanning,
lower-extremity Doppler ultrasound studies, and echocardiography
were all normal. Following this evaluation, the patient was referred to
our institution for further diagnostic evaluation.