Achondroplasia

Achondroplasia is the most common cause of disproportionate short stature, caused by mutations in the FGFR3 gene that impair the normal conversion of cartilage into bone at the growth plates of the long bones. It results in short arms and legs relative to the trunk, a large head with a prominent forehead, and normal intelligence and lifespan for most affected individuals. Roughly eighty percent of cases arise from a new mutation in a child of average-height parents rather than being inherited, and the name comes from Greek roots meaning "without cartilage formation," reflecting the condition's effect on bone growth.