|
|
| DiseaseID |
HGD2 |
| Genetic
Disorder |
Achondroplasia
|
| Gene
Name |
FGFR3 gene |
| Description |
Achondroplasia is a disorder of bone growth. It is the most common form of disproportionate short stature. It occurs in one in every 15,000 to one in 40,000 live births. Achondroplasia is caused by a gene alteration (mutation) in the FGFR3 gene. The FGFR3 gene makes a protein called fibroblast growth factor receptor 3 that is involved in converting cartilage to bone. FGFR3 is the only gene known to be associated with achondroplasia. All people who have only a single copy of the normal FGFR3 gene and a single copy of the FGFR3 gene mutation have achondroplasia.
Most people who have achondroplasia have average-size parents. In this situation, the FGFR3 gene mutation occurs in one parent's egg or sperm cell before conception. Other people with achondroplasia inherit the condition from a parent who has achondroplasia.
|
| Symptoms |
The typical appearance of achondroplastic dwarfism can be seen at birth. Symptoms may include:
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 (frontal bossing) Shortened arms and legs (especially the upper arm and thigh) Short stature (significantly below the average height for a person of the same age and sex) Spinal stenosis Spine curvatures called kyphosis and lordosis
|
| Causes |
Achondroplasia is one of a group of disorders called chondrodystrophies or osteochondrodysplasias.
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. 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, most cases appear as spontaneous mutations. This means that two parents without achondroplasia may give birth to a baby with the condition. |
| Diagnosis |
Achondroplasia is diagnosed by characteristic clinical and X-ray findings in most affected individuals. In individuals who may be too young to make a diagnosis with certainty or in individuals who do not have the typical symptoms, genetic testing can be used to identify a mutation in the FGFR3 gene.
Genetic testing can identify mutations in 99 percent of individuals who have achondroplasia. Testing for the FGFR3 gene mutation is available in clinical laboratories.
|
| Treatment |
No specific treatment is available for achondroplasia. Children born with achondroplasia 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 who have achondroplasia need careful monitoring and support for social adjustment |
|
|
