[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Skeleton, muscles, limbs and skin](https://durgical.com/en/embryology/#a-musculoskeletal) › Achondroplasia (FGFR3) [Embryology](https://durgical.com/en/embryology/) · [Skeleton, muscles, limbs and skin](https://durgical.com/en/embryology/#a-musculoskeletal) # Achondroplasia (FGFR3) - Malformation The most common cause of short stature with short limbs: an overactive gene slows the growth of cartilage in the long bones. Updated 2026-11-01 **See it in 3D:** [Humerus](https://durgical.com/en/anatomy/humerus/) · [Femur](https://durgical.com/en/anatomy/femur/) · [Base of the skull](https://durgical.com/en/anatomy/occipital-bone/) · [L4 vertebra](https://durgical.com/en/anatomy/lumbar-vertebra-spine-and-pelvis-l4/) · [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/) ## Key points - FGFR3 gain of function, autosomal dominant. - Most cases are new mutations (advanced paternal age). - Affects the endochondral skeleton: long bones and skull base; the vault is normal. - Serious risk: narrow foramen magnum in infancy. - Normal intelligence. ## What it is Achondroplasia is the most common skeletal dysplasia, about 1 in 15,000 to 40,000 births. It is caused by a mutation that leaves the FGFR3 receptor overactive, which slows chondrocyte proliferation in the growth plate. It affects bones that ossify by the endochondral route: the limbs and the skull base. Intelligence is normal. ## Embryological cause - FGFR3 is a normal brake on cartilage growth; the gain-of-function mutation leaves it permanently switched on. - Almost all cases are due to the same mutation (G380R) in the transmembrane domain. - Autosomal dominant inheritance; about 80 % are new mutations, linked to advanced paternal age. - It affects endochondral ossification (long bones, vertebrae, skull base); the membranous vault grows normally. - Two mutant copies are usually lethal; other FGFR3 mutations cause thanatophoric dysplasia (lethal) and hypochondroplasia (mild). ## Markers - FGFR3 - G380R - Autosomal dominant ## How it presents - Rhizomelic shortening: upper arms and thighs shorter than forearms and legs. - Macrocephaly with frontal bossing and midface hypoplasia. - Trident hand, marked lumbar lordosis and bowed legs. - Narrow foramen magnum: risk of brainstem compression, apnoea and hydrocephalus in early childhood. - In adults: lumbar spinal stenosis. ## Diagnosis - Third-trimester ultrasound: short femur with a large head; usually not visible before week 24. - X-ray: characteristic pelvis and vertebrae, with the distance between pedicles narrowing downwards. - Molecular testing of FGFR3 confirms the diagnosis. ## Memory aid FGFR3 is the cartilage brake; in achondroplasia the brake is stuck on. ## Test yourself Think of the answer, then tap the question to see it. ## Which gene causes achondroplasia, and what does the mutation do? FGFR3; the mutation makes it overactive and slows chondrocyte proliferation. ## Why is the skull vault normal in achondroplasia? Because it forms by intramembranous ossification, which does not depend on the cartilage growth plate. ## Which early neurological complication is most feared? Brainstem compression from a narrow foramen magnum, which can cause apnoea and hydrocephalus. ## Which parental factor is linked to new FGFR3 mutations? Advanced paternal age. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/achondroplasia/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Humerus](https://durgical.com/en/anatomy/humerus/) - [Femur](https://durgical.com/en/anatomy/femur/) - [Base of the skull](https://durgical.com/en/anatomy/occipital-bone/) - [L4 vertebra](https://durgical.com/en/anatomy/lumbar-vertebra-spine-and-pelvis-l4/) - [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/) ## Related - [Skull: neurocranium, viscerocranium, sutures and fontanelles](https://durgical.com/en/embryology/skull-neurocranium-viscerocranium-sutures-and-fontanelles/) - [Limb development: the apical ectodermal ridge, ZPA and limb rotation](https://durgical.com/en/embryology/limb-development-the-apical-ectodermal-ridge-zpa-and-limb-rotation/) - [Craniosynostosis](https://durgical.com/en/embryology/craniosynostosis/) - [Prenatal diagnosis: ultrasound, serum screening, cell-free DNA, CVS, amniocentesis](https://durgical.com/en/embryology/prenatal-diagnosis-ultrasound-serum-screening-cell-free-dna-cvs-amniocentesis/) - [Congenital hydrocephalus: aqueductal stenosis](https://durgical.com/en/embryology/congenital-hydrocephalus-aqueductal-stenosis/) - [Vertebrae: resegmentation of the sclerotomes](https://durgical.com/en/embryology/vertebrae-resegmentation-of-the-sclerotomes/) ## Related conditions - [Hydrocephalus](https://durgical.com/en/conditions/hydrocephalus/) - [Lumbar spinal stenosis](https://durgical.com/en/conditions/lumbar-spinal-stenosis/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Achondroplasia: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/achondroplasia/) (MedlinePlus, US National Library of Medicine, 2026); Langman's Medical Embryology, 13th ed., ch. 10: The Axial Skeleton (Wolters Kluwer, 2015). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/achondroplasia/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/achondroplasia/