Where on Chromosome is the problem?

Achondroplasia is caused by either an autosomal dominant trait (genes found on chromosomes other than the X and Y) from a parent or a mutation in the FGFR3 gene -- also known as the fibroblast growth receptor. However, 80% of all cases appear to be mutations. The gene is located on the short arm of chromosome, which affects gene's ability to direct proper development and maintenance of bone growth and health.

What is the problem?

The mutation affects the gene's ability to direct and manage bone growth, thus leading to a situation where the effected will have abnormal bone growth. The cartilage that is expected to form into bone fails to do so in those effected with Achondroplasia (this significantly occurs in the humerus and femur). This results in a short body type, commonly known as dwarfism. Those affected with Achondroplasia are also likely to have other health problems because of it. Possible complications include club feet and increased fluid buildup in the brain, known as hydrocephalus. A common issue is also spinal stenosis: "narrowing of the spinal canal that can pinch the upper part of the spinal chord" (NIH Achondroplasia). The disease occurs in 1 in every 15,000 to 40,000 births (depending on birthrate for any given year).

What is the prognosis?

Those afflicted by Achondroplasia seldom reach 5 foot; females average a height of 4 feet and 1 inch while males average a height of 4 feet and 4 inches. Although their physical stature is greatly affected, Achondroplasia patients have normal intellectual capabilities. Those affected tend to have bowed legs, prominent foreheads, and frequent ear infections because of narrow nasal canals. Common problems with children having this disorder are kyphosis (hunch-like back), lordosis (inward curve of lower back), and hypotonia (poor muscle tone). If both parents have the gene, they rarely live longer than a few months; inheriting two forms of this gene results in an "underdeveloped rib cage", leading to their death because of "respiratory failure" (NIH Achondroplasia). However if only one parent has the disease then they have a 50% chance of living beyond the first several months.

Cite Your Sources


NIH Achondroplasia

Medline Plus

Johns Hopkins Medicine

Madison's Foundation