Achondroplasia (patient information)

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Overview
Achondroplasia is a genetic condition that affects about 1 in 25,000 people. It causes a type of dwarfism that in which your arms and legs are short in comparison to your head and trunk. It causes about 70% of all dwarfism.

What are the symptoms of Achondroplasia?
All people with achondroplasia have short stature. The average height of an adult male with achondroplasia is 131 centimeters (4 feet, 4 inches), and the average height for adult females is 124 centimeters (4 feet, 1 inch).

Characteristic features of achondroplasia include:
 * Short stature (significantly below the average height for a person of the same age and sex)
 * An average-size trunk
 * Short arms and legs with particularly short upper arms and thighs
 * Bowed legs
 * Limited range of motion at the elbows
 * An enlarged head (macrocephaly) with a prominent forehead
 * Fingers are typically short and the ring finger and middle finger may diverge, giving the hand a three-pronged (trident) appearance.
 * Spinal stenosis
 * Spine curvatures called kyphosis and lordosis

People with achondroplasia are generally of normal intelligence.

What causes Achondroplasia?
Mutations in the FGFR3 gene cause achondroplasia. The FGFR3 gene provides instructions for making a protein that is involved in the development and maintenance of bone and brain tissue. Two specific mutations in the FGFR3 gene are responsible for almost all cases of achondroplasia. Researchers believe that these mutations cause the protein to be overly active, which interferes with skeletal development and leads to the disturbances in bone growth seen with this disorder.

Achondroplasia is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. 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%.

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

Individuals who inherit two altered copies of this gene typically have very severe problems with bone growth, and are usually stillborn or die shortly after birth from respiratory failure.

Who is at highest risk?
A person is most likely to be affected by achondroplasia if one or both of his parents are affected by it. 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%.

When to seek urgent medical care?
If there is a family history of achondroplasia and you plan to have children, you may find it helpful to speak to your health care provider.

Diagnosis
Achondroplasia can be diagnosed during pregnancy or immediately after birth.

During pregnancy, a prenatal ultrasound may show excessive amniotic fluid surrounding the unborn infant. Examination of the infant after birth shows increased front-to-back head size. There may be signs of hydrocephalus ("water on the brain"). Additionally, x-rays of the long bones can reveal achondroplasia in the newborn.

Treatment options
There is no specific treatment for achondroplasia. Related abnormalities, including spinal stenosis and spinal cord compression, should be treated when they cause problems.

Where to find medical care for Achondroplasia?
Directions to Hospitals Treating Achondroplasia

What to expect (Outlook/Prognosis)?
People with achondroplasia seldom reach 5 feet in height. Intelligence is in the normal range.

Dwarfism itself is not a disease. However, there is a greater risk of some health problems for people affected by Dwarfism. With proper medical care, most people with dwarfism have active lives and live as long as other people.

Infants who receives the abnormal gene from both parents do not often live beyond a few months.

Possible complications
Health problems commonly associated with achondroplasia include episodes in which breathing slows or stops for short periods (sleep apnea), obesity, and recurrent ear infections. In adulthood, individuals with the condition usually develop a pronounced and permanent sway of the lower back (lordosis) and bowed legs. Older individuals often have back pain, which can cause difficulty with walking.

Other complications can include:
 * Clubbed feet
 * Fluid buildup in the brain (hydrocephalus)

Prevention
Genetic counseling may be helpful for prospective parents when one or both have achondroplasia. However, because achondroplasia most often develops spontaneously, prevention is not always possible.