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Biosimilar Switching — SCE Rheumatology MCQ

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HardRheumatology PharmacologyBiosimilar SwitchingSCE Rheumatology

A 52-year-old woman has recurrent metatarsal stress fractures, two poorly healing femoral pseudofractures and premature loss of adult teeth. Her DXA T-score is -2.7, but alkaline phosphatase has been below the laboratory reference range on every measurement. Before treating the apparent osteoporosis, what is the safest next step?

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Correct answer: E — Withhold bisphosphonate; confirm the low alkaline phosphatase, measure pyridoxal-5-phosphate and refer for hypophosphatasia assessment

Explanation lettering: E = shown as A · A = shown as D · D = shown as E

D is correct. Persistently low alkaline phosphatase, premature tooth loss and metatarsal or femoral pseudofractures are a classic adult hypophosphatasia pattern. The result should be confirmed, secondary causes considered, pyridoxal-5-phosphate measured and specialist biochemical/genetic assessment arranged before osteoporosis treatment. A and B risk worsening defective mineralisation with a bisphosphonate. C introduces an unconfirmed treatment plan before the metabolic bone diagnosis is established. E investigates possible contributors to low alkaline phosphatase but then proceeds to another antiresorptive without resolving the diagnostic concern.

Reference: International consensus on diagnosis and treatment of hypophosphatasia: https://pmc.ncbi.nlm.nih.gov/articles/PMC11811241/