A 27-year-old man presents to the emergency department with complaints of chest pain and hemoptysis. He has a history of chronic sinusitis and recurrent pneumonias, requiring multiple hospitalizations. He also reports infertility, stating that he and his wife have been unable to conceive despite years of trying. On physical examination, heart sounds are auscultated on the right side, and the patient confirms that he has situs inversus. Pulmonary function tests reveal a decreased FEV1/FVC ratio, consistent with obstructive lung disease, and a CT scan of the chest demonstrates dilated bronchioles with a signet-ring appearance and situs inversus. What is the underlying microscopic defect in this patient’s disorder?
