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Achondroplasia is characterized by abnormal bone growth that results in short stature with disproportionately short arms and legs, a large head, and characteristic facial features with frontal bossing and mid-face hypoplasia. In infancy, hypotonia is typical, and acquisition of developmental motor milestones is often delayed. Intelligence and life span are usually normal, although compression of the spinal cord and/or upper airway obstruction increases the risk of death in infancy.


  • Abnormal hand appearance with persistent space between the long and ring fingers
  • Bowed legs
  • Decreased muscle tone
  • Disproportionately large head-to-body size difference
  • Prominent forehead
  • Shortened arms and legs
  • Short stature
  • Spinal stenosis
  • Spine curvatures called kyphosis and lordosis

  • Causes:
    It is caused by a mutation in a gene (called fibroblast growth factor receptor 3) that is located on chromosome 4 (6, 7). In a minority of cases, a child inherits this disease from a parent who also has the condition. If one parent has the condition and the other does not, there is a 50 percent chance that their child will be affected. If both parents have it, there is a 50 percent chance that the child will inherit the condition, a 25 percent chance that the child will not have it, and a 25 percent chance that the child will inherit one abnormal gene from each parent and have severe skeletal abnormalities that lead to early death. A child who does not inherit the condition cannot pass it on to his or her own children.

    In more than 80 percent of cases, it is not inherited but results from a new mutation that occurs in the egg or sperm cell that forms the embryo(4). Typically, these parents have no other children with achondroplasia, and the chances of their having a second affected child are extremely small.

    Geneticists have observed that older-than-average fathers (age 40 and older) are more likely to have children with this disease and certain other autosomal dominant conditions (disorders that occur when one gene in a gene pair is abnormal) caused by new mutations. Individuals with it resulting from new mutations transmit the disorder to their children as described above.

    No specific treatment is available. Children born with this need to have their height, weight and head circumference monitored using special growth curves standardized for achondroplasia. Measures to avoid obesity at an early age are recommended.

    A magnetic resonance imaging (MRI) or CT scan may be needed for further evaluation of severe muscle weakness (hypotonia) or signs of spinal cord compression. To help with breathing, surgical removal of the adenoids and tonsils, continuous positive airway pressure (CPAP) by nasal mask, or a surgical opening in the airway (tracheostomy) may be needed to correct obstructive sleep apnea.

    When there are problems with the lower limbs, such as hyperreflexia, clonus or central hypopnea, then surgery called suboccipital decompression is performed to decrease pressure on the brain.

    Children need careful monitoring and support for social adjustment.

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    ...less medical jargon in a 'Quick Glance' format!