A genetic disorder of bone growth and the most common cause of short stature with disproportionately short arms and legs (known as dwarfism). The individual has a large head with a prominent forehead (frontal bossing); underde- velopment (hypoplasia) of the midface, with cheek- bones that lack prominence; and a low nasal bridge with narrow nasal passages. The fingers are short, and the ring and middle fingers diverge to give the hand a trident (three-pronged) appearance. The brain is entirely normal in people with achon- droplasia, but complications can damage the brain and spinal cord. Achondroplasia is an autosomal dominant trait, affecting boys and girls equally. Most cases are due to new gene mutations that appear for the first time in the affected child. Achondroplasia is caused by mutation in the fibroblast growth factor receptor-3 gene (FGFR3), and prenatal diagnosis is possible.