A 33-year-old man has had increasing dyspnea for the past 8 years. He does not smoke. On examination, there are decreased breath sounds over lower lung fields. A chest radiograph shows flattened diaphragms; his CT scan is shown in the figure. Pulmonary function tests show decreased DLCO, decreased FEV1, and increased FVC. Arterial blood gas analysis shows Po2, 65 mm Hg; Pco2, 60 mm Hg; HCO3–, 32 mEq/L; and pH, 7.35. A sibling is similarly affected. What is the most likely mechanism for his pulmonary disease?