How do genetics affect achondroplasia?
Achondroplasia is the most common form of short-limbed dwarfism. It affects about one in every 15,000 babies. More than 80% of the time, these babies have parents who are average height. It is impossible to know simply by looking at parents if their child will have achondroplasia. Achondroplasia is caused by a change (mutation) in the gene called fibroblast growth factor receptor 3 (FGR3). This mutation is often what doctors call “spontaneous” — it is not a change passed down by parents who have the condition themselves. The mutation is more likely to occur in the sperm of fathers older than age 35. A protein called fibroblast growth factor (FGF) stimulates and controls how cartilage grows. It helps determine both the length and shape of bones. When FGR3 is not normal, the fibroblast growth factor cannot work the way it usually does.
