Achondroplasia

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Achondroplasia

Definition:

Achondroplasia is a 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 or osteochondrodysplasias.

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The disorder causes a type of dwarfism that is recognized by a 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 may be inherited as an autosomal dominant trait, which means that if a child gets the defective gene from one parent, the child will have the disorder.

However, approximately 80% of cases appear as spontaneous mutations. This means that two parents without achondroplasia may give birth to a baby with achondroplasia. 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%.