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 or osteochondrodysplasias. 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%.

Signs and tests

Examination of the infant shows increased front-to-back head size ( occipital-frontal circumference ). There may be signs of hydrocephalus associated with enlargement of the chambers within the center of the brain (ventricular dilatation). Tests that identify achondroplasia include: X-rays of the long bones (see bone X-ray ) can demonstrate achondroplasia in the newborn.


There is no specific treatment for achondroplasia. Associated orthopedic abnormalities such as club feet should be corrected.

Expectations (prognosis)

People with achondroplasia seldom reach five feet in height. Mentality is normal. Infants who are homozygous for achondroplasia (both parents are achondroplastic and each has contributed an affected gene ) seldom live beyond a few months.


  • hydrocephalus
  • club feet
  • Calling your health care provider

    Call for an appointment with your health care provider if you are planning to have children and there is a family history of achondroplasia.


    Genetic counseling may be helpful for prospective parents when one or both have achondroplasia. Because achondroplasia arises as a spontaneous mutation, absolute prevention is not possible.

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