Achondroplasia

Definition:

An inherited disorder of bone growth that causes the most common type of dwarfism.

Causes, incidence, and risk factors:

Achondroplasia is an inherited disorder of bone growth. It is one of the group of disorders that are collectively called chondrodystrophies. The disorder causes a type of dwarfism that is recognized by its characteristic normal- to large-sized head, shortened arms and legs (especially the upper arm and thigh), a normal-sized trunk and waddling gait. Achondroplasia is the most common type of dwarfism.

Achondroplasia is inherited as an autosomal dominant trait. However, the majority of cases, approximately 80%, appear as spontaneous mutations. If one parent has achondroplasia, the infant has a 50% chance of inheriting the disorder. If both parents have the condition, the infant's chances of being affected increase to 75%.