What is the Cause of Achondroplastic Dwarfism?

The cause of achondroplasia is a mutation of the FGFR3 gene. The term achondroplasia translates to ‘without cartilage formation’. In people with achondroplastic dwarfism, the protein that forms bones fails to do its part, which affects normal skeletal development.

This common form of skeletal dysplasia affects only 1 - 9 individuals among 1,00,000 people worldwide. It causes dwarfism where the size of the torso is normal with short arms and legs. Though usually a result of sporadic mutation, it can also be inherited.

Read here to find out in detail about the condition, its symptoms, treatments and more.

Things to Know About FGFR3 Gene and Its Mutation

The primary function of the FGFR3 gene is to instruct the creation of Fibroblast Growth Factor Receptor 3, which is responsible for bone growth. However, when someone suffers from achondroplasia disease this gene sends constant instructions to slow down bone growth in the limbs.

Therefore, the process of ossification is hampered. In simple terms, the condition makes the body unable to convert cartilage into bones. This leads to achondroplastic dwarfism. Among the various causes of dwarfism, achondroplasia accounts for over 90% of the cases.

Is Achondroplastic Dwarfism Always Inherited?

There is a common misconception among people that this type of genetic condition is hereditary and is passed down from parents. However, achondroplastic dwarfism is different. It can be categorised into 3 unique types or ways of occurrence.

De Novo Mutation

In 80% of cases, achondroplasia is not hereditary and affects children of parents who have average height. It occurs spontaneously from a new genetic mutation. Moreover, it is also unlikely for these parents to have another child affected by achondroplasia.

Autosomal Dominant Mutation

However, there is a 50% chance of achondroplasia inheritance if one parent has the condition. In fact, around 20% of people with this condition have at least one parent who suffers from achondroplastic dwarfism.

Homozygous Achondroplasia

In case both parents have achondroplasia, there is a 25% chance that their children will be of average stature and a 50% chance that they will inherit the condition. However, there is also a 25% chance of the child getting homozygous achondroplasia, which is fatal.

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What Are the Symptoms of Achondroplasia?

All achondroplasia symptoms are physical. However, the symptoms and the health problems that the individual faces might slightly vary by age.

How Do Doctors Diagnose Achondroplasia?

Using ultrasounds, doctors can detect before birth if the baby's arms and legs are disproportionate. However, in most cases, doctors cannot confirm achondroplasia before birth. Here are ways how achondroplasia is diagnosed:

1. Prenatal examination in case both parents are affected
2. Physical examination
3. X-rays, MRI, CT scans
4. FGFR3 gene testing

What Are the Ways to Treat Achondroplastic Dwarfism?

There is no specific achondroplasia treatment, but only ways to manage the symptoms. The condition has no cure. However, to live a full and healthy life, it is essential to mitigate potential complications. The ways to do that are as follows:

1. Managing weight through healthy eating habits.
2. Ventriculoperitoneal shunt, a surgery to reduce the fluid pressure on the brain.
3. Adenoids and tonsil removal surgery.
4. Use of CPAP nasal masks for apnea and antibiotics or ear tubes to control infection.
5. Using growth hormones.

How Is Achondroplasia Different From Marfan Disease?

Like achondroplastic dwarfism is a result of stunted bone growth, Marfan syndrome makes the connective tissues too elastic and loose. The main features of Marfan syndrome are long limbs and slender fingers and toes.  Other differences include:

Final Words

Along with managing the symptoms, it is also important to cater to the mental health of an individual with achondroplastic dwarfism. A welcoming environment that provides emotional support and group socialising boosts confidence.

Also, proper educational support and tools such as a step stool can help reduce problems caused by physical challenges. Lastly, if you have breathing issues, frequent ear infections, or limb aches, visit a healthcare centre immediately.

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Frequently Asked Questions

Is there any way to reduce the risk of achondroplasia?

There is no way to reduce the risk of achondroplasia. It is a rare genetic condition caused by a spontaneous and new gene mutation. However, if a parent has achondroplastic dwarfism, they can reduce the chance of passing it on by using preimplantation genetic testing.

What is preimplantation genetic testing?

Preimplantation genetic testing, or PGT, is a procedure to check if there are any genetic mutations in the embryo. It is only possible on embryos that are created using In Vitro Fertilisation (IVF). After passing the screening, it is transferred to the uterus.

Is achondroplasia the same as midgetism?

The word ‘midget’ is a highly offensive and outdated term used to describe a person of short stature. Achondroplasia is a genetic condition that causes stunted bone growth, resulting in dwarfism.

How is the trident hand identified?

One can identify trident hands by features such as short and stubby fingers. The fingers are almost of equal length and form a fork-like structure because of the clear separation between the middle and ring fingers.

What medications stimulate growth in people with achondroplasia?

Various new medicines such as vosoritide have received approval in some regions and are being used to stimulate growth in children with achondroplasia who can still grow. However, it is mandatory to seek professional medical guidance before use.

How do doctors perform FGFR3 gene testing?

FGFR3 gene testing requires samples such as Amniotic Fluid, Peripheral Blood (EDTA), Chorionic Villus (CVS), or Cord Blood (EDTA). This test can be done for adults and children, at the prenatal stage, to rule out the chances of achondroplasia.

What is hydrocephalus?

Along with short limbs, children with achondroplastic dwarfism also have a large head. This is the result of accumulation of cerebrospinal fluid (CSF) in the ventricles. This happens as the spine narrows and prevents CSF from flowing in and out of the skull.

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