The patient was admitted to the hospital in November 2005 for worsening dyspnea associated with weight gain, abdominal distension, and bilateral lower extremity edema. Transesophageal echocardiography estimated the RVSP to be 105 mm Hg. Agitated saline solution contrast failed to reveal a shunt. Laboratory examination revealed no evidence of autoimmune disease or HIV infection. Pulmonary function test results revealed normal spirometric volumes (FVC, 2.52 L [95%]; FEV1, 1.83 L [88%]; and FEV1/FVC ratio, 73%); air-trapping (total lung capacity, 119%; residual volume, 160%, and residual volume/total lung capacity ratio, 50%); decreased diffusing capacity (71%), and increased airway resistance (3.62 cm H2O/L/s). Room air arterial blood gas levels (Pao2, 78 mm Hg) and nocturnal oximetry (low arterial oxygen saturation, 89%) failed to reveal significant hypoxemia.