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Achondroplasia FGFR3 mutation — MRCPCH TAS MCQ

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ModerateGeneticsAchondroplasia FGFR3 mutationMRCPCH TAS

A term newborn has rhizomelic limb shortening, frontal bossing and a normal birth weight. Both parents have average stature and there is no family history. What is the most likely explanation?

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Correct answer: D — A de novo activating FGFR3 mutation

Achondroplasia is most often caused by a de novo activating mutation in FGFR3, which inhibits endochondral bone growth. Collagen type I defects cause osteogenesis imperfecta rather than disproportionate short-limbed dwarfism. A useful pearl is that advanced paternal age is associated with new dominant mutations such as FGFR3 variants.

Reference: Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi; The Science of Paediatrics MRCPCH Mastercourse