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Obesity hypoventilation syndrome — USMLE Step 3 MCQ

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ModerateInternal Medicine (chronic management)Obesity hypoventilation syndromeUSMLE Step 3

A 51-year-old man with BMI 48 kg/m2 has daytime sleepiness and morning headaches. Oxygen saturation is 91% while awake. Arterial blood gas shows PaCO2 52 mm Hg. Pulmonary function testing shows no obstruction. Which of the following is the most likely diagnosis?

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Correct answer: A — Obesity hypoventilation syndrome

Obesity with awake hypercapnia after exclusion of other causes is consistent with obesity hypoventilation syndrome.

Reference: American Thoracic Society Obesity Hypoventilation Guideline