The children present a disproportionately large skull, they have a narrow and long face, red cheeks, a prominent forehead, a pointed chin… Here are some visible physical elements of the rare disease called Sotos syndrome, which is also expressed by developmental delay due to cognitive impairment. Explanations.
Who does it affect, where does it come from?
It is estimated that approximately 1 in every 14,000 births has Sotos syndrome. It can affect both boys and girls and is present from birth.
“In more than 95% of cases, Sotos syndrome is due to mutations or microdeletions in the NSD1 gene (5q35), which plays a role in growth and development.“, notes the site Orpha.net. But another genetic anomaly may also be responsible, bi-alleic mutations of the APC2 gene (19p13.3).
What are the symptoms of Sotos syndrome?
Sotos syndrome has physical symptoms: it manifests as excessive growth, which can be present from birth. The subjects have a big skulla long and narrow face, a prominent forehead, sparse hair on the forehead linea pointed chin, suffer from hypertelorism (excessive spacing of the orbits).
Babies can suffer fromhypotonia, meaning they lack muscle tone. They may have difficulty feeding. “Sotos syndrome is associated with mild to moderate intellectual disability, as well as a wide spectrum of behavioral disorders. A delay is frequently observed in the acquisition of developmental milestones“. The child can also be the victim of convulsions. Once an adult, the subjects are tall. More rarely, deafness, genitourinary or cardiac abnormalities are detected.
Risks of transmission, prenatal diagnosis
If it is known that the genetic mutation exists in the family, it is possible to establish a prenatal diagnosis, via a genetic analysis of the fetus. The risk is estimated to be 50% of transmitting it to the baby when the gene is carried by one of the two parents. Even though, “the vast majority of patients are carriers of de novo mutations; the risk of recurrence is then very low“, notes Orpha.net.
To diagnose it, if there is a suspicion of Sotos syndrome, the method is based on observing the clinical signs first. Certain diseases with similar symptoms must be ruled out, such as Malan’s overgrowth syndrome, Weaver’s syndrome, Tatton-Brown-Rahman’s syndrome,… Then, to confirm, molecular screening for pathogenic genes is performed.
Consequences and treatments
This disease does not affect the life expectancy of patients. It has an impact on the physical appearance of the subject as well as on his intellectual capacities. The extent of the consequences is difficult to estimate, because some patients are completely independent, while others are not. Currently, there is no treatment for this disease. It can simply be taken care of, in a multidisciplinary way, to help the patient to develop or to evolve in daily life.
Sources:
- Orpha.net, the portal for rare diseases and orphan drugs
- EM Consult