Achondroplasia is the most common type of short-limbed dwarfism. The condition occurs in 1 in 15,000 to 40,000 newborns.
Achondroplasia is the most commonly occurring abnormality of bone growth (skeletal dysplasia), occurring in approximately 1 in 20,000-30,000 live births. This genetic disorder is caused by a change (mutation) in the fibroblast growth factor receptor 3 (FGFR3) gene. Achondroplasia occurs as a result of a spontaneous genetic mutation in approximately 80 percent of patients; in the remaining 20 percent it is inherited from a parent. This genetic disorder is characterized by an unusually large head (macrocephaly), short upper arms (rhizomelic dwarfism), and short stature (adult height of approximately 4 feet). Achondroplasia does not typically cause impairment or deficiencies in mental abilities. If the bones that join the head and neck do not compress the brainstem or upper spinal cord (craniocervical junction compression), life expectancy is near normal.
In the early stages of development, much of the fetal skeleton is made up of cartilage tissue, which turns into bone. Achondroplasia occurs when cartilage tissue doesn't develop in the bones of your arms and legs. This genetic disorder leads to short-limb dwarfism with the upper parts of arms and legs shorter than the lower portions of those limbs (rhizomelic shortening).
What is the difference between achondroplasia and skeletal dysplasia (dwarfism)?
Achondroplasia is the most common form of skeletal dysplasia, which is the umbrella term used to identify hundreds of conditions that affect the growth of bones and cartilage. Achondroplasia specifically targets bone growth in your arms and legs.
Is achondroplasia hereditary?
- Most cases of achondroplasia are not inherited. Anyone can be affected by achondroplasia. Around 80% of individuals with achondroplasia have parents of normal height and are born with a new gene alteration (de novo mutation). It is rare that these parents will have another child with achondroplasia.
- Only one parent needs to pass down the gene for a child to be born with achondroplasia (autosomal dominant). There is a 50% chance of a person with achondroplasia and a partner who does not have achondroplasia having a child with the disorder.
- If both parents have achondroplasia, there is a 25% chance that the child will be born with homozygous achondroplasia, which leads to stillbirth or death shortly after birth.
How does achondroplasia affect my child’s body?
Infants born with achondroplasia normally have weak muscle tone (hypotonia), which could delay motor skill development. There’s is also a high risk of spinal cord compression and upper respiratory blockages among infants, which increases the risk of health complications.
It is common for people with achondroplasia to have breathing problems, recurrent ear infections and be prone to obesity. All children with achondroplasia should be carefully monitored regularly by a healthcare provider to treat or prevent any symptoms that may arise.
What are the symptoms of achondroplasia?
- Bones are shortened (thigh, upper arm)
- Short hands and feet
- Large separation between third and fourth fingers
- Maximum height of 4-ft
- Head larger than normal
- Prominent forehead
- Flat nose
- Delayed development in infants (sitting, crawling, walking)
