Trisomy 21 syndrome

Trisomy 21 Syndrome
Down_Syndrome_Chromosome_21.png
Synonyms	Down syndrome
Pronounce	N/A
Specialty	N/A
Symptoms	Intellectual disability, characteristic facial features, developmental delays
Complications	Congenital heart defects, gastrointestinal issues, thyroid dysfunction
Onset	Prenatal
Duration	Lifelong
Types	N/A
Causes	Genetic disorder
Risks	Advanced maternal age
Diagnosis	Karyotype analysis, prenatal screening
Differential diagnosis	N/A
Prevention	N/A
Treatment	Supportive care, educational interventions
Medication	N/A
Prognosis	N/A
Frequency	1 in 700 births
Deaths	N/A

Trisomy 21 Syndrome, commonly known as Down syndrome, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability.

Etiology

Trisomy 21 is caused by an error in cell division called nondisjunction, which results in an embryo with three copies of chromosome 21 instead of the usual two. This can occur during meiosis in the formation of the egg or sperm, or during mitosis after fertilization.

Epidemiology

Trisomy 21 is one of the most common chromosomal abnormalities in humans, occurring in approximately 1 in 700 live births. The risk of having a child with Down syndrome increases with advanced maternal age, particularly in mothers over the age of 35.

Clinical Features

Individuals with Trisomy 21 often exhibit a range of clinical features, including:

• Hypotonia (decreased muscle tone)
• Distinctive facial features such as a flat facial profile, upward slanting eyes, and a single transverse palmar crease
• Short stature
• Developmental delay and intellectual disability
• Increased risk of congenital heart defects, particularly atrioventricular septal defect
• Gastrointestinal anomalies such as duodenal atresia
• Increased risk of thyroid dysfunction, particularly hypothyroidism
• Higher susceptibility to respiratory infections and leukemia

Diagnosis

Diagnosis of Trisomy 21 can be made prenatally or postnatally. Prenatal screening includes:

• Ultrasound for nuchal translucency
• Maternal serum screening for specific markers
• Non-invasive prenatal testing (NIPT) using cell-free fetal DNA

Definitive diagnosis is made through karyotype analysis, which can be performed via:

• Chorionic villus sampling (CVS)
• Amniocentesis

Management

There is no cure for Trisomy 21, but early intervention and supportive care can improve quality of life. Management includes:

• Regular health check-ups to monitor for common complications
• Early intervention programs to address developmental delays
• Special education and vocational training
• Surgical correction of congenital anomalies, if necessary
• Treatment of associated medical conditions such as hypothyroidism

Prognosis

The life expectancy of individuals with Trisomy 21 has increased significantly with advances in medical care. Many individuals live into their 60s, although life expectancy can be affected by the presence of congenital heart defects and other health issues.

Social and Ethical Considerations

The diagnosis of Trisomy 21 raises important social and ethical considerations, including decisions about prenatal testing and the provision of resources and support for affected individuals and their families.

See Also

• Genetic counseling
• Intellectual disability
• Congenital heart defect