Achondroplasia is caused by a sporadic/spontaneous (sudden genetic defect) mutation in the Fibroblast Growth Factor Receptor 3 gene (FGFR3 gene)
Location of FGFR3 gene: short arm of Chromosome 4 (4p16.3)
The FGFR3 gene codes for the protein that codes for the development and maintenance of bone and brain tissue, and determines the shape and health of bones.
If there is a mutation in this protein, then the development and growth of bone cells will be disrupted, resulting in Achondroplasia.
The FGFR3 gene mutation occurs in one parent's sperm or egg cell before conception or during the development of the fetus.
In early fetal development, the skeleton is mostly made up of cartilage. Usually, most of this cartilage turns into bone later on, but in people with Achondroplasia, a lot of the cartilage does not turn into bone.
Etiology
People with Achondroplasia may develop knee or back problems due to problems caused by their short stature
They may also neurological problems due to spinal cord compression
It may also cause Apnea or brief periods where breathing is slowed or stopped
It also causes hydrocephalus or a condition in which fluid accumulates in the brain, enlarging the head and damaging the brain
Achondroplasia also decreases muscle tone, which causes a delay in learning how to walk or learn other motor skills
Achondroplasia does not shorten life span or cause learning disabilities