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Sarcoidosis-related hypercalcemia — ABIM Board MCQ

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HardPulmonary/Critical CareSarcoidosis-related hypercalcemiaABIM Board

A 41-year-old Black woman has fatigue, cough, and ankle pain. Chest radiograph shows bilateral hilar lymphadenopathy. Serum calcium is 11.5 mg/dL, PTH is suppressed, 25-hydroxyvitamin D is normal, and 1,25-dihydroxyvitamin D is elevated. Transbronchial biopsy shows noncaseating granulomas. Which of the following is the most likely cause of hypercalcemia?

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Correct answer: D — Granulomatous macrophage-mediated conversion of vitamin D to calcitriol

Sarcoid granulomas contain activated macrophages with extrarenal 1-alpha hydroxylase activity, increasing calcitriol and intestinal calcium absorption. Suppressed PTH helps exclude primary hyperparathyroidism.

Reference: ATS Sarcoidosis Diagnosis and Management Guidance