Achondroplasia

Achondroplasia is an inherited skeletal dysplasia, usually caused by a variant in FGFR3. It limits growth of long bones, producing disproportionate short stature and shortened limbs.

FGFR3: FGFR3 is a receptor tyrosine kinase that regulates cell growth and cartilage development. Activating variants in this receptor usually cause achondroplasia by restraining growth-plate activity.
Autosomal dominant inheritance: Autosomal dominant inheritance occurs when one altered copy of a gene can cause a trait or disorder. One FGFR3 variant is sufficient, though many affected children inherit a variant from neither parent.
Achondroplasia clinical practice guidelines: Achondroplasia clinical practice guidelines are recommendations for monitoring and managing health across the lifespan. They organize surveillance for complications such as sleep apnea, spinal stenosis, and hearing problems.
Hypochondroplasia: Hypochondroplasia is a genetic skeletal dysplasia causing relatively mild disproportionate short stature, often involving FGFR3. It can resemble achondroplasia but typically has milder features and less distinctive radiographic findings.
Endochondral ossification: Endochondral ossification forms bone by replacing a cartilage template. Achondroplasia chiefly disrupts this process in the growth plates of long bones.
De novo mutation: A de novo mutation is a genetic change first arising in an individual rather than inherited from a parent. Most achondroplasia cases arise this way, often in the paternal germline.
Sleep apnea: Sleep apnea is repeated interruption or reduction of breathing during sleep. Airway anatomy and neurologic complications can increase risk, making sleep assessment part of care.
Thanatophoric dysplasia: Thanatophoric dysplasia is a severe, usually perinatal-lethal skeletal dysplasia caused by activating FGFR3 variants. It involves the same signaling pathway but causes far more severe skeletal and respiratory impairment.
Growth plate: A growth plate is cartilage near the end of a growing bone where longitudinal growth occurs. Excess FGFR3 signaling slows growth-plate cartilage expansion in achondroplasia.
Skeletal dysplasia: A skeletal dysplasia is a genetic disorder affecting bone or cartilage growth and development. Achondroplasia is one defined disorder within this broad group.

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