Is Floating-Harbor syndrome hereditary?

Floating-Harbor syndrome is a rare genetic condition almost exclusively caused by de novo (spontaneous) mutations, meaning it is typically not inherited from parents. While it is a genetic disorder, it is rarely hereditary in the traditional sense, as the vast majority of cases occur sporadically in individuals with no prior family history of the condition.

Is Floating-Harbor syndrome hereditary?

To understand the genetics of Floating-Harbor syndrome, it is important to distinguish between "genetic" and "hereditary." A condition is genetic if it is caused by a change in DNA, but it is only hereditary if it is passed down from a parent to a child. Floating-Harbor syndrome is caused by heterozygous mutations in the SRCAP gene. In the overwhelming majority of documented cases, these mutations are de novo—they occur spontaneously in the egg or sperm cell at the time of conception. Because the mutation is not present in the parents' own genetic makeup, the condition is usually not hereditary.

What is the risk of recurrence for parents?

Because most cases of Floating-Harbor syndrome are de novo, the risk of recurrence for parents who have one affected child is considered very low, generally estimated to be less than 1%. However, because the possibility of germline mosaicism (where the mutation exists in a small percentage of a parent's reproductive cells) cannot be entirely ruled out, genetic counseling is strongly recommended for families planning future pregnancies. In the rare event that a parent is affected by Floating-Harbor syndrome, the condition would follow an autosomal dominant inheritance pattern, meaning there would be a 50% chance of passing the SRCAP mutation to each child.

How is Floating-Harbor syndrome diagnosed genetically?

Diagnosis of Floating-Harbor syndrome is confirmed through molecular genetic testing. If a physician suspects the syndrome based on clinical features—such as characteristic facial features, delayed speech, and short stature—they will typically order testing that specifically analyzes the SRCAP gene. Common testing methods include:

• Single-gene sequencing: Targeted analysis of the SRCAP gene.


• Multi-gene panel: A broader test that sequences many genes associated with developmental delay and short stature simultaneously.


• Whole Exome Sequencing (WES): Often used when clinical presentation is complex or when initial targeted tests are negative.

The role of genetic counseling for families

Genetic counseling is a vital step for any family navigating a diagnosis of Floating-Harbor syndrome. A genetic counselor can help interpret test results, explain the implications of de novo mutations, and provide support for the emotional aspects of a rare disease diagnosis. For the 11 community members currently connected through DiseaseMaps.org, genetic counseling has served as a bridge between clinical findings and long-term family planning. Counselors can also discuss prenatal options, such as amniocentesis or chorionic villus sampling (CVS), for parents who have a confirmed family history of the condition and wish to pursue reproductive options.

Next steps

• Consult with a clinical geneticist to confirm the diagnosis through molecular SRCAP testing.


• Schedule an appointment with a genetic counselor to discuss the recurrence risk specific to your family's genetic profile.


• Connect with the Floating-Harbor syndrome community at DiseaseMaps.org to share experiences and find peer support.


• Review your child's clinical history with a multidisciplinary team, including a pediatrician and speech-language pathologist, to manage developmental milestones.

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 regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Floating-Harbor syndrome.


• Orphanet: Floating-Harbor syndrome (ORPHA:3379).


• OMIM (Online Mendelian Inheritance in Man): Floating-Harbor syndrome; FHS (MIM #136140).


• National Center for Biotechnology Information (NCBI) GeneReviews: SRCAP-Related Disorders.