Dwarfism or “achondroplasia” is a congenital growth disorder characterized by abnormal bone development and resulting in short stature and shorter limbs.
Definition: what is dwarfism?
We talk about “dwarfism” but medically it isachondroplasia. “It’s a rare genetic pathologylinked to a lack of growth of cartilage and bone tissue, explains Dr. Geneviève Baujat, pediatrician-geneticist, specialist in constitutional bone diseases, at the Necker-Enfants Malades hospital in Paris. It concerns approximately 1 in 2,500 people without ethnic or geographical predominance. It is characterized by the association of a short stature, short limbs and extremities, and possible frontal bulging“.
From what size?
When talking about dwarfism, the maximum height in adulthood is generally 1m50.
What causes achondroplasia (dwarfism)?
Achondroplasia is of genetic origin. “It is due to a specific mutation of the FGFR 3 gene, present on chromosome 4, which plays a role in the development of cartilage, says Dr. Baujat. Most of the time it is a “new” mutation, not transmitted, and there is no family history”. There are other causes of small constitutional sizes: implications of other genes necessary for growth programming, metabolic, renal or digestive pathologies, growth hormone deficiency…
What are the symptoms ?
- A predominant small size on the limbs and extremities: the people concerned have a smaller size than those of the same age and same sex
- Dorsal kyphosis and/or lumbar hyperlordosis
- Possibly curved lower limbs
- Limitations of the opening of the elbows
- Pain in the legs, neck and lumbar region
- In adolescents and adults, tingling and tingling in the lower extremities during long-distance walking.
- Respiratory and cardiac disorders (sleep apnea): the functioning of these systems can be disturbed by the deformation of the spine in the cervical region and at the level of the upper airways.
90% of people with the disease do not have any sick relatives in their family history.
Proportionate or disproportionate dwarfism?
“Achondroplasia is characterized by a predominant growth defect in the upper limbs, less marked in the lower limbs, and barely noticeable in the trunk. It is a “disproportionate” dwarfism”, says Dr. Baujat. Other causes of constitutional shortness are said to be “proportionate” when the deficit is harmonious at all body segments.
Is it hereditary?
90% of people with the disease do not have any sick relatives in their family history. “But a person with achondroplasia has a probability of 50% transmission with each pregnancy“, warns our expert.
During the screening ultrasound for the third trimester of pregnancy, the diagnosis can be discussed and confirmed in a prenatal center of expertise. Otherwise, it will be at birth or, more rarely, during childhood. “Clinical signs and imaging can confirm the diagnosis and the molecular study will often be carried out, as part of a genetic consultation, to support the diagnosis”, adds Dr. Baujat. Thereafter, follow-up is coordinated by a clinical geneticist in pediatric age and by a rheumatologist in adulthood.
What is the life expectancy?
This disease does not affect life expectancy.
Thanks to Dr. Geneviève Baujat, pediatrician-geneticist, specialist in constitutional bone diseases, at the Necker-Enfants Malades hospital, in Paris.