National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

IQSEC2


Other Names:
IQSEC2-related intellectual disability; IQSEC2-related epilepsy; X-linked intellectual disability 1/78; IQSEC2-related intellectual disability; IQSEC2-related epilepsy; X-linked intellectual disability 1/78; X-linked intellectual disability 1; X-linked intellectual disability 78 See More
IQSEC2 is a genetic condition that causes intellectual disability and sometimes other physical, neurological, or psychiatric symptoms.[1] People with this condition can have seizures that are often difficult to control with medications. Other symptoms may include motor and language development delay, regression of learning abilities, autistic-like behavior, characteristic hand movements, and behavioral problems. Physical features may include abnormal head shape (plagiocephaly), very small head (microcephaly), reduced muscle tone (hypotonia), and crossed eyes (strabismus). This condition is caused by mutations in the IQSEC2 gene, which is located on chromosome X.[1][2][3] Depending on the severity of the gene mutation, the features can range from only intellectual disability to a syndrome that includes the other symptoms. In general, males are more affected than females.[1] Most cases are not inherited from a parent but are caused by a new (de novo) mutation. When the condition is inherited, the pattern is called X-linked recessive. There is no specific treatment, but early intervention and other services can support development. Seizure medications such as lamotrigine and rufinamide have been reported to control seizures in some people.[4]
Last updated: 7/25/2017

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Showing of 10 |
Medical Terms Other Names
Learn More:
HPO ID
5%-29% of people have these symptoms
Postnatal microcephaly 0005484
Seizure 0001250
Percent of people who have these symptoms is not available through HPO
Brachycephaly
Short and broad skull
0000248
Generalized hypotonia
Decreased muscle tone
Low muscle tone
[ more ] 		0001290
Hypermetropia
Farsightedness
Long-sightedness
[ more ] 		0000540
Intellectual disability
Mental deficiency
Mental retardation
Mental retardation, nonspecific
Mental-retardation
[ more ] 		0001249
Poor speech 0002465
Strabismus
Cross-eyed
Squint
Squint eyes
[ more ] 		0000486
X-linked dominant inheritance 0001423
X-linked recessive inheritance 0001419
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Last updated: 7/1/2020

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Social Networking Websites

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

In-Depth Information

  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • PubMed is a searchable database of medical literature and lists journal articles that discuss IQSEC2. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Alexander-Bloch AF, McDougle CJ, Ullman Z & Sweetser DA. IQSEC2 and X-linked syndromal intellectual disability. Psychiatr Genet. June 2016; 26(3):101-108. https://www.ncbi.nlm.nih.gov/pubmed/27010919.
  2. Gandomi SK, Farwell Gonzalez KD, Parra M et al. Diagnostic exome sequencing identifies two novel IQSEC2 mutations associated with X-linked intellectual disability with seizures: implications for genetic counseling and clinical diagnosis. J Genet Couns. June 2014; 23(3):289-298. https://www.ncbi.nlm.nih.gov/pubmed/24306141.
  3. Tran Mau-Them F, Willems M, Albrecht B, et al. Expanding the phenotype of IQSEC2 mutations: truncating mutations in severe intellectual disability. European Journal of Human Genetics. 2014; 22(2):289-292. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3895633/.
  4. Zerem A, Haginoya K, Lev, D. et al. The molecular and phenotypic spectrum of IQSEC2-related epilepsy. Epilepsia. 2016; 57:1858-1869. https://www.ncbi.nlm.nih.gov/pubmed/27665735.