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Vitamin D osteomalacia — SCE Rheumatology MCQ

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ModerateMetabolic bone diseaseVitamin D osteomalaciaSCE Rheumatology

A 39-year-old woman presents with diffuse bone pain, bony tenderness and difficulty rising from a chair. Serum 25-hydroxyvitamin D is 14 nmol/L, corrected calcium 2.08 mmol/L, phosphate 0.62 mmol/L and alkaline phosphatase 310 IU/L. Renal function is normal. Vitamin D-deficiency osteomalacia is diagnosed. Which is the most appropriate initial disease-specific treatment?

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Correct answer: A — Colecalciferol replacement, with calcium supplementation as required

The correct answer is A. Proximal myopathy, diffuse bone tenderness, severe 25-hydroxyvitamin D deficiency, hypophosphataemia, low calcium and raised alkaline phosphatase are characteristic of vitamin D-deficiency osteomalacia. Treatment must restore mineralisation with a therapeutic course of native vitamin D, usually colecalciferol, while ensuring adequate calcium intake and supplementing calcium when clinically required. Alfacalcidol is not first-line when renal vitamin D activation is intact. Phosphate alone does not correct the underlying vitamin D deficiency and is principally relevant to phosphate-depletion or renal phosphate-wasting osteomalacia. Teriparatide and alendronic acid are osteoporosis therapies; neither is appropriate as initial monotherapy for an unmineralised osteoid disorder.

Reference: NHS, Rickets and osteomalacia, treatment section, last reviewed 9 July 2025. https://www.nhs.uk/conditions/rickets-and-osteomalacia/