软骨发育不全症(Achondroplasia)是一种显性遗传病，患者位于第四对染色体上基因「纤维芽细胞生长因子第三号接受体」出现缺陷，引致骨骼发育不良，身材极度矮小、鼻梁塌陷、脊椎弯曲、手指脚趾粗短、下肢较短且常呈Ｏ型腿等现象，大多数患者的智能完全正常。

其发生率为1/25000至1/40000。

遗传方面，其绝大多数是因为基因突变所致、也有由单基因从一代传给下一代、精子或卵子在形成时发生FGFR-3的基因突变或父母一方有软骨发育不全。

Achondroplasia is a common cause of dwarfism. It occurs as a sporadic mutation in approximately 80% of cases (associated with advanced paternal age) or it may be inherited as an autosomal dominant genetic disorder.

People with achondroplasia have short stature, with an average adult height of 131 centimeters (52 inches) for males and 123 centimeters (48 inches) for females. Achondroplastic adults are known to be as short as 62.8 cm (24.7 in). If both parents of a child have achondroplasia, and both parents pass on the mutant gene, then it is very unlikely that the homozygous child will live past a few months of its life. The prevalence is approximately 1 in 25,000.