skip to main content

Sarcoidosis Hypercalcaemia — RACP Adult Medicine MCQ

Instant feedback + full explanation. One question, done properly.

ModerateRespiratorySarcoidosis HypercalcaemiaRACP Adult Medicine

A 30-year-old woman presents with progressive dyspnoea and bilateral hilar lymphadenopathy. Bronchoscopic BAL shows a CD4/CD8 ratio of 6:1 (elevated). Transbronchial biopsy shows non-caseating granulomas. Serum calcium is 2.82 mmol/L. What is the mechanism of hypercalcaemia in sarcoidosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Unregulated extra-renal 1-alpha-hydroxylation of vitamin D by activated macrophages

In sarcoidosis, activated macrophages within granulomas express 1-alpha-hydroxylase, converting 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D (calcitriol) in an unregulated fashion. This increases intestinal calcium absorption and bone resorption, leading to hypercalcaemia (occurring in ~10% of cases) and hypercalciuria (~30%). PTH is suppressed. Treatment includes corticosteroids (which inhibit the 1-alpha-hydroxylase), avoidance of sunlight/vitamin D supplements, and adequate hydration.

Reference: eTG – 2025 – Respiratory; eTG – 2025 – Endocrinology