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Paget Disease Biochemistry — SCE Rheumatology MCQ

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EasyMetabolic Bone DiseasePaget Disease BiochemistrySCE Rheumatology

A 55-year-old man has persistent pain in the right tibia. Radiographs show cortical thickening, trabecular coarsening and bony expansion, and a radionuclide bone scan demonstrates metabolically active Paget disease involving the right tibia and pelvis. Liver function, renal function and vitamin D status are normal. Which biochemical pattern is most likely?

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Correct answer: B — Raised alkaline phosphatase with normal adjusted calcium, phosphate and parathyroid hormone

The correct answer is B. Active Paget disease produces markedly accelerated, coupled bone resorption and formation. Increased osteoblast activity raises bone-derived alkaline phosphatase, while adjusted calcium, phosphate and PTH are usually normal because systemic mineral homeostasis is preserved. Total ALP, interpreted alongside liver function tests, is the standard first-line biochemical marker of metabolic activity and can help assess response to treatment. ALP may be normal in limited monostotic disease, but a substantial rise is expected with the extensive active disease described. Hypercalcaemic patterns in B and C suggest another process; immobilisation-related hypercalcaemia is an uncommon complication rather than the characteristic profile. D and E suggest phosphate or vitamin D deficiency with secondary hyperparathyroidism.

Reference: Ralston SH et al. Diagnosis and Management of Paget's Disease of Bone in Adults: A Clinical Guideline. Journal of Bone and Mineral Research. 2019;34:579–604. https://pubmed.ncbi.nlm.nih.gov/30803025/