A 19-year-old man with a history of chronic lung problems dies due to respiratory distress after a prolonged episode of pneumonia. Autopsy shows dilation of the bronchial tree, which extends almost to the pleural surface. Many of the small airways are filled with mucin plugs containing abundant inflammatory cells and debris. Which of the following is the most likely cause of this patient's autopsy findings?

Question

A 19-year-old man with a history of chronic lung problems dies due to respiratory distress after a prolonged episode of pneumonia.  Autopsy shows dilation of the bronchial tree, which extends almost to the pleural surface.  Many of the small airways are filled with mucin plugs containing abundant inflammatory cells and debris.  Which of the following is the most likely cause of this patient's autopsy findings?

Quizplus · Accepted Answer

11ec160b_3a0c_ee8d_9249_3f9cdc3ff9ca_MD0001_00 This patient with chronic lung problems has autopsy findings consistent with cystic fibrosis (CF), an autosomal recessive disorder caused by a genetic mutation (eg, ΔF508) affecting the CF transmembrane conductance regulator. A defect in this chloride channel prevents normal hydration of mucus and results in the accumulation of thick, viscous secretions throughout the body (eg, lungs, pancreas, vas deferens). Respiratory disease, the most common CF manifestation, is the predominant cause of morbidity and mortality. Patients typically have chronic cough due to impaired clearance of inspissated secretions in the bronchioles. This buildup leads to mucus plugging (ie, obstructive lung disease), bacterial colonization (ie, recurrent pneumonia), and chronic infiltration of inflammatory cells. Over time, elastase produced by neutrophils causes bronchiectasis (weakened, dilated bronchial walls) and parenchymal destruction. Advanced disease is associated with irreversible damage, progressive respiratory failure, and shortened life expectancy. (Choice A) Accumulation of proteinaceous material within alveoli occurs with pulmonary alveolar proteinosis, a condition in which clearance of surfactant by alveolar macrophages is impaired. Inflammatory cells are not present in this disorder. (Choice B) Antigen-mediated aggregation of macrophages describes the formation of granulomas, as occurs with Mycobacterium tuberculosis and Histoplasma capsulatum infection. The inciting organism can usually be identified on microscopy and mucus plugs are not characteristically present. (Choice C) Deficiency of alpha-1 antitrypsin (protease inhibitor of elastase) causes liver dysfunction, emphysema, and eventually bronchiectasis. The onset of pulmonary symptoms typically occurs at age >20, and mucus plugs would not be expected. (Choice E) Increased pulmonary venous pressure is characteristic of left-sided heart failure, which results in pulmonary congestion and interstitial and alveolar edema. Bronchiectasis is not an associated finding. Educational objective: Cystic fibrosis is an autosomal recessive disorder in which a defective chloride channel causes impaired clearance of thick, viscous airway secretions. Patients typically develop a chronic cough, recurrent pulmonary infections, and bronchiectasis (dilated bronchial tree).

A 19-Year-Old Man with a History of Chronic Lung Problems