9q34.3 deletion syndrome

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Obesity, Sleep & Internal medicine
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9q34.3 deletion syndrome
Synonyms	Kleefstra syndrome
Pronounce
Specialty	Medical genetics
Symptoms	Intellectual disability, developmental delay, hypotonia, distinctive facial features
Complications	N/A
Onset	Congenital
Duration	Lifelong
Types	N/A
Causes	Genetic mutation
Risks
Diagnosis	Genetic testing, chromosomal microarray analysis
Differential diagnosis	Angelman syndrome, Prader-Willi syndrome, Smith-Magenis syndrome
Prevention
Treatment	Supportive care, speech therapy, occupational therapy
Medication
Prognosis	Variable
Frequency	Rare
Deaths

9q34.3 deletion syndrome is a rare genetic disorder characterized by the deletion of a small segment of the long arm of chromosome 9, specifically at the 9q34.3 location. This deletion can lead to a variety of clinical features, including developmental delay, intellectual disability, and distinctive facial features. The syndrome is also associated with Kleefstra syndrome, which is caused by mutations or deletions affecting the EHMT1 gene located in the same chromosomal region.

Genetics

The 9q34.3 deletion syndrome is caused by a deletion of genetic material on the long arm of chromosome 9. This deletion typically includes the EHMT1 gene, which plays a crucial role in histone methylation and gene expression. The loss of this gene's function is believed to be responsible for many of the clinical features observed in individuals with the syndrome. The syndrome is usually inherited in an autosomal dominant manner, meaning that a single copy of the deleted region is sufficient to cause the disorder. However, most cases result from a de novo deletion, meaning that the deletion occurs spontaneously and is not inherited from either parent.

Clinical Features

Individuals with 9q34.3 deletion syndrome often present with a range of clinical features, which can vary in severity. Common features include:

• Developmental delay: Affected individuals may experience delays in reaching developmental milestones such as sitting, walking, and talking.
• Intellectual disability: The degree of intellectual disability can vary, but most individuals have mild to moderate impairment.
• Distinctive facial features: These may include a flat midface, upslanting palpebral fissures, a short nose, and a thin upper lip.
• Hypotonia: Reduced muscle tone is common, which can affect motor skills and coordination.
• Behavioral issues: Some individuals may exhibit behavioral problems, including autism spectrum disorder traits.

Diagnosis

Diagnosis of 9q34.3 deletion syndrome is typically confirmed through genetic testing, such as chromosomal microarray analysis or fluorescence in situ hybridization (FISH). These tests can identify the specific deletion on chromosome 9 and help differentiate it from other genetic disorders with overlapping features.

Management

There is no cure for 9q34.3 deletion syndrome, and treatment is primarily supportive and symptomatic. Management strategies may include:

• Early intervention programs: These can help address developmental delays and improve outcomes.
• Special education services: Tailored educational programs can support learning and development.
• Speech and occupational therapy: These therapies can assist with communication skills and daily living activities.
• Behavioral therapy: Interventions may help manage behavioral issues and improve social skills.

Prognosis

The prognosis for individuals with 9q34.3 deletion syndrome varies depending on the severity of symptoms and the presence of any associated health issues. With appropriate support and interventions, many individuals can lead fulfilling lives.

See also

• Kleefstra syndrome
• Chromosome 9
• Genetic disorder
• Intellectual disability