Respiratory System MCAT Practice Question
A 58-year-old man with a 15-year history of poorly controlled type 2 diabetes mellitus presents for pulmonary function testing as part of a comprehensive diabetes complications screening. His HbA1c is 9.2%. Physical examination is notable for diabetic retinopathy and microalbuminuria. Spirometry is normal, but single-breath diffusing capacity for carbon monoxide (DLCO) is 62% of predicted. Hemoglobin is 14.2 g/dL. A chest radiograph shows no infiltrates, effusions, or cardiac enlargement. Which of the following best explains this patient's reduced DLCO?
Answer choices
- ABasement membrane thickening from non-enzymatic glycation of collagen in the blood-gas barrierCorrect answer
- BPulmonary edema resulting from increased capillary hydrostatic pressure due to diabetic cardiomyopathy
- CInterstitial fibrosis from chronic inflammation and transforming growth factor-beta activation
- DVentilation-perfusion mismatch secondary to small airway disease and mucus plugging
- EReduced pulmonary capillary blood volume from microvascular thrombosis
- FDecreased alveolar surface area from emphysematous destruction in this former smoker
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