Achondroplasia: a disorder of bone growth. (Symptoms of Achondroplasia…
Achondroplasia: a disorder of bone growth.
Causes of Anchondroplasia
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.
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 of Achondroplasia
short stature with disproportionately short arms and legs
a large head (macrocephaly)
specific facial features with a prominent forehead (frontal bossing)
Infants born with achondroplasia typically have weak muscle tone (hypotonia) causing delays in walking and other motor skills
breathing problems in which breathing stops or slows down for short periods (apnea)
recurring ear infections
pronounced and permanent sway of the lower back (lordosis)
problems with the lower back can cause back pain leading to difficulty with walking.
Achondroplasia is diagnosed by characteristic clinical and X-ray findings in most affected individuals.
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 of Achondroplasia
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.
Heredity of Achondroplasia
Most cases of achondroplasia are not inherited. When achondroplasia is inherited, it is inherited in an autosomal dominant manner
A person who has achondroplasia who is planning to have children with a partner who does not have achondroplasia has a 50 percent chance, with each pregnancy, of having a child with achondroplasia.
When both parents have achondroplasia, the chance for them, together, to have a child with normal stature is 25 percent. Their chance of having a child with achondroplasia is 50 percent.