Is Sotos Syndrome hereditary?

Sotos syndrome is a genetic condition that is almost always caused by a new (de novo) mutation rather than being inherited from a parent. While it is technically a genetic disorder caused by changes in the NSD1 gene, it is rarely hereditary in the sense of being passed down through generations, meaning the risk to siblings of an affected child is typically very low.

Is Sotos syndrome hereditary or genetic?

There is an important clinical distinction between a condition being "genetic" and "hereditary." Sotos syndrome is a genetic disorder because it is caused by an alteration in the NSD1 gene (located on chromosome 5q35). However, it is rarely hereditary. In the vast majority of cases, Sotos syndrome occurs as a de novo mutation, meaning the genetic change happens spontaneously during the formation of the egg or sperm, or very early in embryonic development. Because the mutation is not present in the parents’ DNA, it is not usually inherited from them.

What is the risk of recurrence for families?

Because most cases of Sotos syndrome arise from new mutations, the risk of recurrence for parents who have one child with the condition is extremely low—generally estimated at less than 1%. In very rare instances, a parent may carry a balanced chromosomal rearrangement or a mosaic mutation (where only some body cells carry the gene change) that could increase the risk of having another child with Sotos syndrome. Due to this possibility, clinical geneticists often recommend parental testing even if the child’s mutation appears de novo.

How is Sotos syndrome diagnosed through genetics?

Genetic testing is the gold standard for confirming a diagnosis of Sotos syndrome. Testing typically involves molecular genetic analysis of the NSD1 gene. The following methods are commonly utilized by clinical geneticists:

• Sequence analysis: To detect point mutations, small deletions, or insertions within the NSD1 gene.


• Deletion/duplication analysis: To identify larger deletions of the NSD1 gene or the 5q35 region, which account for approximately 10–15% of cases.


• Chromosomal microarray (CMA): Often the first-tier test if the diagnosis is suspected but not yet confirmed, as it can detect larger genomic imbalances.

What is the role of genetic counseling?

Genetic counseling is vital for any family navigating a diagnosis of Sotos syndrome. A genetic counselor can help interpret test results, calculate recurrence risks based on family history, and discuss reproductive options. For those planning future pregnancies, options such as prenatal diagnosis (via chorionic villus sampling or amniocentesis) or preimplantation genetic testing (PGT) may be discussed. Because 98 people with Sotos syndrome have already shared their experiences on DiseaseMaps.org, many families find comfort and practical insights by connecting with this community during the counseling process.

Next steps

• Consult with a board-certified clinical geneticist to confirm the diagnosis and discuss specific mutation results.


• Request a referral for genetic counseling to review family planning options and recurrence risks.


• Connect with the Sotos syndrome community on DiseaseMaps.org to share experiences and find peer support.


• Review updated clinical guidelines on the NIH GARD website to stay informed about the latest research and monitoring recommendations.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Sotos syndrome overview.


• Orphanet: Rare disease database entry for Sotos syndrome (ORPHA:844).


• OMIM (Online Mendelian Inheritance in Man): Entry #117550, Sotos syndrome 1.


• Sotos Syndrome Support Association (SSSA): Clinical resources and patient support information.