Achondroplasia - Causes, Symptoms and Treatments

What is Achondroplasia?
Achondroplasia is an autosomal dominant (an autosomal dominant gene occurs on an autosomal also known as non-sex determining chromosome) genetic disorder related to bone growth and causes growth hormone deficiency and also is a common cause known for dwarfism (most commonly short limb dwarfism) in human beings.

This disorder is found in ,1 in every 15,000 to 30,000 newborns. People born with this medical condition remain short in height throughout their lives, where an average height for male and female suffering from this disorder is not more than 4 feet and 2 to 3 inches. Generally the male suffering from this disorder is found to be 1-2 inches taller than the female in the same age group. Except for the height and a couple of things, people suffering from this disorder have almost the same characteristics (including lifespan and intelligence) as any other normal human being.

What causes Achondroplasia?
As mentioned above, this disorder is an autosomal dominant genetic disorder i.e. this disorder is caused due to abnormalities in the autosomal dominant gene found on autosomal chromosome. Study also shows that some kind of chemical changes in the gene can lead to this disorder in a newborn. It’s not necessarily related to any particular activity or conditions that parent’s of newborn go through when the mother is pregnant and even it’s not necessarily caused only due to genetic reasons, it actually starts with the mutation in genes right from the moment of conception. It also makes difference if one of or both the parents are carrying the affected/mutated gene (Fibroblast Growth Factor Receptor 3 - FGFR3) on the probability of their child carrying this disorder. Also, a single copy of altered gene (mutation in gene) in each cell is sufficient to cause this disorder in a person.

Recent studies have shown that the gene mutation is passed on through inheritance during spermatogenesis. Another study has shown that this disorder is caused by multiple (at least two different) mutations in the FGFR3, by G to A point mutation at nucleotide 1138 leading to glycine to arginine substitution, and in very rare cases it is caused due to G to C mutation at nucleotide 1138.

How is Achondroplasia diagnosed?
Diagnostic methods for this disorder are grouped based on the prenatal (before birth) diagnosis and diagnosis based on a patient’s post-natal physical and other conditions. Prenatal diagnosis involves DNA test to confirm homozygosity, parental ultrasound test etc.

Other diagnosis includes identification of hypotonia (low muscle tone) and slow motor movement which is characterized by inability or delay in walking even 24 to 34 months after birth, obesity in children, infection of middle ear (otitis media) because of drainage of the tube that connects the middle ear and throat (this condition is caused due to abnormal skull structure development), overcrowding and misalignment (malocclusion) of the teeth, abnormal teeth orientation etc. as a result of abnormal skull structure development, bow legs (Genu Varum), shortening of arms and legs, improper development of elbow extension, development of Thoracolumbar gibbus, deformed bones of hands and legs etc. are the physical conditions which are related to achondroplasia.

Skull structure abnormality and other internal problems (such as abnormal vertebral bodies, congenitally narrowed spinal canal, small squared iliac wings, narrow sciatic notch and horizontal acetabular roof, short and thick tubular bones etc.) are diagnosed with the help of skeletal survey. Abnormal skull structure with narrow foramen magnum and relatively small skull base is associated with achondroplasia. Medical imaging methods such as radiology, MRI, CT scan etc. are used to study skeletal structure.

Treatment
Symptoms based treatments are used to help people suffering from achondroplasia. Measurements to keep obesity under control, middle ear infection management/treatment, surgery in some severe cases such as extreme need for limb lengthening, straightening and corrective surgery for other deformed bone conditions etc. are also used to help people suffering from achondroplasia.

Along with the above mentioned treatments, people suffering from this disorder also need social and mental support, which can prove to be much more important.