Is Koolen De Vries Syndrome / 17q21.31 Microdeletion Syndrome hereditary?

Koolen-de Vries syndrome, also known as 17q21.31 microdeletion syndrome, is a genetic condition that is almost always the result of a de novo (spontaneous) mutation rather than being inherited from parents. While it is a genetic disorder, it is rarely hereditary, meaning most affected individuals are the first in their family to have the condition.

Is Koolen-de Vries syndrome hereditary?

In the vast majority of cases, Koolen-de Vries syndrome is not hereditary. It is caused by a submicroscopic deletion or a mutation of the KANSL1 gene on chromosome 17q21.31. Because these genetic changes typically occur spontaneously during the formation of reproductive cells (sperm or egg) or in early fetal development, they are classified as de novo events. This means that neither parent usually carries the genetic alteration, and the recurrence risk for future pregnancies is generally very low—less than 1%.

How is Koolen-de Vries syndrome diagnosed?

Diagnosis of Koolen-de Vries syndrome is achieved through specialized genetic testing. Because the deletion is often too small to be seen on a standard karyotype, clinicians use high-resolution testing methods to confirm the diagnosis:

• Chromosomal Microarray (CMA): The gold standard for detecting the characteristic 17q21.31 microdeletion.


• Whole Exome Sequencing (WES): Used to identify specific point mutations within the KANSL1 gene if a microarray is negative.


• FISH (Fluorescence In Situ Hybridization): Sometimes used to confirm specific structural changes identified by other methods.

What is the role of genetic counseling for families?

Genetic counseling is highly recommended for families affected by Koolen-de Vries syndrome. A genetic counselor can help interpret test results, provide accurate recurrence risk assessments, and discuss reproductive options. For the rare instances where a parent is found to carry a balanced chromosomal rearrangement that predisposes them to having a child with Koolen-de Vries syndrome, the risk may be higher, and options such as Preimplantation Genetic Testing (PGT) can be explored.

Next steps

• Consult with a clinical geneticist to review diagnostic test results.


• Connect with the 8 members currently sharing experiences with Koolen-de Vries syndrome on DiseaseMaps.org.


• Request a referral to a genetic counselor to discuss family planning and recurrence risks.


• Visit the Koolen-de Vries Syndrome Foundation for peer support and the latest research updates.

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

References

• NIH Genetic and Rare Diseases Information Center (GARD): 17q21.31 microdeletion syndrome.


• Orphanet: Koolen-de Vries syndrome (ORPHA: 261235).


• OMIM (Online Mendelian Inheritance in Man): #610443 - Koolen-de Vries Syndrome.


• Koolen-de Vries Syndrome Foundation: Clinical resources and patient support.