Which are the causes of Autosomal recessive multiple pterygium syndrome / Escobar syndrome?

TL;DR: Autosomal recessive multiple pterygium syndrome, also known as Escobar syndrome, is a genetic disorder caused by mutations in the CHRNG gene. It is inherited in an autosomal recessive pattern, meaning an individual must inherit two copies of the mutated gene—one from each parent—to manifest the condition.

What is the genetic cause of Escobar syndrome?

The primary cause of Autosomal recessive multiple pterygium syndrome is a disruption in the CHRNG gene, which provides instructions for making a subunit of the acetylcholine receptor. This receptor is essential for the communication between nerve cells and muscles. When this gene is mutated, muscle development during fetal growth is significantly impaired, leading to the characteristic webbing (pterygia) and joint contractures seen in Escobar syndrome.

Is Autosomal recessive multiple pterygium syndrome hereditary?

Yes, Autosomal recessive multiple pterygium syndrome is strictly a genetic condition. It follows an autosomal recessive inheritance pattern, which can be broken down as follows:

• Carrier Parents: Both parents are typically unaffected carriers, meaning they each have one functional copy and one mutated copy of the CHRNG gene.


• 25% Chance: With each pregnancy, there is a 25% probability that the child will inherit two mutated copies and develop Escobar syndrome.


• 50% Chance: There is a 50% probability the child will be an asymptomatic carrier like the parents.


• 25% Chance: There is a 25% probability the child will inherit two functional copies of the gene.

Are there environmental or external triggers?

There are no known environmental, dietary, or lifestyle triggers for Autosomal recessive multiple pterygium syndrome. Because the condition is rooted in the fetal development of muscle and connective tissue, it cannot be caused by maternal actions or external infections. It is important to distinguish that while "risk factors" for some diseases involve lifestyle choices, the only "risk factor" for Escobar syndrome is the biological inheritance of specific genetic variants from both parents.

What is the current state of research?

While the link between the CHRNG gene and Autosomal recessive multiple pterygium syndrome is well-established, ongoing research focuses on understanding the variability in clinical severity. Researchers are investigating how different specific mutations within the CHRNG gene result in the wide spectrum of physical presentations observed in patients.

Next steps

• Consult with a clinical geneticist to discuss family planning and carrier testing.


• Connect with the 2 community members on DiseaseMaps.org who share lived experience with Autosomal recessive multiple pterygium syndrome.


• Schedule an evaluation with a pediatric orthopedist or a neurologist specializing in neuromuscular disorders.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Multiple Pterygium Syndrome, Escobar Type.


• Online Mendelian Inheritance in Man (OMIM): Entry #265000 (Multiple Pterygium Syndrome, Escobar Type).


• Orphanet: Multiple Pterygium Syndrome, Autosomal Recessive.