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Obstructive sleep apnoea — SCE Respiratory MCQ

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HardSleep MedicineObstructive sleep apnoeaSCE Respiratory

A patient with pulmonary sarcoidosis has corrected calcium 2.92 mmol/L, suppressed PTH and a high-normal 25-hydroxyvitamin D. Which mechanism is responsible?

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Correct answer: B — Macrophage 1-alpha-hydroxylase produces excess calcitriol

Activated macrophages within granulomas express unregulated extrarenal 1-alpha-hydroxylase, converting 25-hydroxyvitamin D to calcitriol and increasing intestinal calcium absorption. Vitamin-D supplementation can worsen hypercalcaemia; significant disease is treated by controlling sarcoid inflammation, usually with corticosteroid.

Reference: BTS Clinical Statement on pulmonary sarcoidosis (Published 2020): https://www.brit-thoracic.org.uk/document-library/clinical-statements/sarcoidosis/bts-sarcoidosis-clinical-statement/; BTS Clinical Statement on pulmonary sarcoidosis (Published 2021): https://thorax.bmj.com/content/76/1/4