Achondroplasia actually is a special type of chondrodyplasia, either is a form of narrowing and / or lengthening of the limbs. This disease is characterized by:

– rhizomelia: which affects the root of the limbs, either the thigh or the arms;

– hyper-lordosis: accentuation of dorsal curvatures;

– brachydactyly: abnormally small size of the phalanges of the fingers and / or toes;

– macrocephaly: abnormally large size of the cranial perimeter;

– hypoplasia: delayed growth of a tissue and / or an organ.

Ethnologically, achondroplasia means “without the formation of cartilage”. This cartilage is a hard but flexible tissue forming part of the composition of the skeleton. Nevertheless, in this pathology, it is not a question of a bad formation at the level of the cartilage but of a problem in the ossification (formation of bones). This applies more to long bones, such as the arms and legs.

The subjects affected by achondroplasia testify to a small build. The average height of a man with achondroplasia is 1,31 m and that of a sick woman is 1,24 m.

The peculiar characteristics of the disease result in a large size of the trunk, but an abnormally small size of the arms and legs. Conversely, macrocephaly is generally associated, which is defined by an enlargement of the cranial perimeter, in particular of the forehead. The fingers of these patients are usually small with a visible divergence of the middle finger, resulting in the shape of the trident hand.

There are certain health problems that can be associated with achondroplasia. This is particularly the case of respiratory anomalies with breathing that is seen to slow down by spurts with periods of apnea. In addition, obesity and ear infections are often associated with the disease. Postural problems are also visible (hyper-lordosis).

Potential complications can arise, such as spinal stenosis, or narrowing of the spinal canal. This results in compression of the spinal cord. These complications are usually signs of pain, weakness in the legs and tingling sensations.

In lesser frequency, the appearance of hydrocephalus (severe neurological abnormality) is possible. (2)

It is a rare disease, the prevalence of which (number of cases in a given population at a given time) is 1 in 15 births. (000)

The clinical manifestations of achondroplasia are manifested at birth by:

– abnormally small size of the limbs with rhizomelia (damage to the roots of the limbs);

– an abnormally large size of the trunk;

– an abnormally large size of the cranial perimeter: macrocephaly;

– hypoplasia: delayed growth of a tissue and / or an organ.

A delay in motor skills is also significant of the pathology.

Other consequences may be associated, such as sleep apnea, recurrent ear infections, hearing problems, dental overlaps, thoracolumbar kyphosis (deformation of the spine).

In the most severe cases of the disease, a compression of the spinal cord can be related to it causing situations of apnea, a delay in development and pyramidal signs (all disorders of motor skills). In addition, hydrocephalus is also plausible leading to neurological deficits and cardiovascular disease.

People with the disease have an average height of 1,31 m for men and 1,24 m for women.

In addition, obesity is widely found in these patients. (1)

The origin of achondroplasia is genetic.

Indeed, the development of this disease results from mutations within the FGFR3 gene. This gene enables the formation of the protein that is involved in the development and regulation of bone and brain tissue.

There are two specific mutations in this gene. According to the scientists, these mutations in question cause too much activation of the protein, interfering with the development of the skeleton and leading to bone deformities. (2)

The disease is transmitted by an autosomal dominant process. Or, that only one of the two copies of the mutated gene of interest is sufficient for the subject to develop the associated sick phenotype. Patients with achondroplasia then inherit a copy of the mutated FGFR3 gene from one of the two sick parents.

By this mode of transmission, there is therefore a 50% risk of transmitting the disease to the offspring. (1)

Individuals inheriting both mutated copies of the gene of interest develop a severe form of the disease resulting in severe limb and bone narrowing. These patients are usually born prematurely and die soon after birth from respiratory failure. (2)

The risk factors for the disease are genetic.

In fact, the disease is transmitted via an autosomal dominant transfer relating to the FGFR3 gene.

This principle of transmission reflects that the unique presence of a single copy of the mutated gene is sufficient for the development of the disease.

In this sense, an individual with one of his two parents suffering from this pathology has a 50% risk of inheriting the mutated gene, and thus also developing the disease.

The diagnosis of the disease is first of all differential. Indeed, in view of the various associated physical characteristics: rhizomelia, hyper-lordosis, brachydactyly, macrocephaly, hypoplasia, etc. the doctor can hypothesize the disease in the subject.

Associated with this first diagnosis, genetic tests make it possible to highlight the possible presence of the mutated FGFR3 gene.

The treatment of the disease begins with a consequent prevention. This helps prevent the development of complications, which can be fatal, in patients with achondroplasia.

Surgery for hydrocephalus is often necessary in newborns. In addition, other surgical procedures can be performed in order to lengthen the limbs.

Ear infections, ear infections, hearing problems, etc. are treated with adequate medication.

Prescribing speech therapy courses can be useful for certain sick subjects.

Adenotonsillectomy (removal of the tonsils and adenoids) may be performed in the treatment of sleep apnea.

Added to these treatments and surgeries, nutritional monitoring and diet are generally recommended for sick children.

The life expectancy of the sick is slightly lower than the life expectancy of the general population. In addition, the development of complications, in particular cardiovascular, can have negative consequences on the vital prognosis of patients. (1)