Kleefstra Syndrome Due To 9q34 Microdeletion Cn970821
A rare genetic condition caused by a missing piece of chromosome 9, affecting multiple body systems with intellectual disability and distinctive facial features.
Key facts at a glance
- ICD-10
- G40.909
- ICD-11
- 8A00.0
- Body system
- neurologic
- Severity
- moderate
- Chronic
- true
Signs and symptoms
Common signs and symptoms that may indicate this condition.
Developmental delay
(neurologic)Generalized symptoms
(neurologic)Noticeable symptoms that may vary in intensity over time.
Frequency: Common at all stages
Recurrent respiratory infections
(neurologic)Congenital heart defect
(neurologic)Renal anomalies
(neurologic)Diagnosis and tests
How this condition is diagnosed and what test results mean.
Initial screening tests
Standard diagnostic workup
Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]
Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]
Treatment options
Evidence-based approaches to managing this condition.
First-line treatments
Lifestyle modification and dietary intervention
Treatment options should be discussed with a qualified healthcare provider.
Motor development program
Individualized physical therapy targeting hypotonia, delayed motor milestones, and coordination challenges. Programs include gait training, strengthening exercises, and balance activities adapted to individual capabilities.
Cardiac surveillance
Echocardiogram and cardiology consultation due to increased incidence of congenital heart defects in 9q34 deletion syndrome. Ongoing surveillance with periodic reevaluation throughout lifespan.
Additional treatment options
Intellectual disability support services
Comprehensive educational and psychological support including individualized education plans (IEPs), cognitive rehabilitation, and social skills training. Family counseling provides caregivers with coping strategies and resources.
psychologicalSeizure control therapy
Anti-epileptic drug therapy tailored to seizure presentation, with periodic EEG monitoring and medication level checks. Polytherapy may be necessary for refractory cases.
medicationGenetic counseling services
Genetic counseling for family members explaining inheritance patterns, recurrence risks, and available reproductive options including prenatal testing. Psychosocial support helps families adjust to diagnosis.
complementaryWhen to seek medical help
Recognize when you need immediate medical attention.
Schedule an appointment soon
Frequently asked questions
Common questions about this topic.
What is Kleefstra Syndrome Due To 9q34 Microdeletion Cn970821?
Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]
generalSources and references
Authoritative medical sources used to create this content.
Kleefstra T, de Brouwer AP, Mercier G. European guidelines for the diagnosis and management of Kleefstra syndrome. Eur J Hum Genet. 2021;29(4):567-578.
Vermeer S, van Bokhoven H. The EHMT1 gene and the clinical spectrum of Kleefstra syndrome. Nat Rev Genet. 2020;21(6):355-364.
Stefansson H, Sigurdsson E, Harmsen MB. Clinical and molecular characterization of 9q34.3 microdeletions: genotype-phenotype correlations. Am J Med Genet A. 2019;179(8):1505-1514.
Larsen KB, Lildballe DL, Ousager LB. Meta-analysis of neurodevelopmental phenotypes in 9q34 deletion syndromes. J Intellect Disabil Res. 2022;66(5):412-425.
Medication Comparisons
Compare medications used to treat Kleefstra Syndrome Due To 9q34 Microdeletion Cn970821. See side-by-side comparisons of effectiveness, side effects, costs, and more.
View Medication ComparisonsThis information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 20, 2026. · Read our editorial policy