Down syndrome

Down syndrome is a genetic disorder caused by the presence of an extra full or partial copy of chromosome 21. This additional genetic material leads to developmental changes and physical characteristics typical of Down syndrome. It is the most prevalent chromosomal disorder, causing lifelong intellectual disability and developmental delays, and is often associated with various medical conditions such as heart and gastrointestinal disorders.

Symptoms and Features

Individuals with Down syndrome exhibit a range of symptoms and physical features, which vary in severity. Common features include:

• Facial Characteristics: Flattened face, small head, short neck, protruding tongue, upward slanting eyelids, and small ears.
• Musculoskeletal Differences: Poor muscle tone, broad and short hands with a single crease in the palm, short fingers, and small hands and feet.
• Growth Patterns: Short height and slow growth.
• Distinctive Eye Features: Tiny white spots on the iris (Brushfield's spots).
• Flexibility: Excessive flexibility in joints.

While some people with Down syndrome have significant health problems, such as serious heart defects, others may be healthy and live fulfilling lives.

Intellectual Disabilities

Cognitive impairment in individuals with Down syndrome typically ranges from mild to moderate. Language development is often delayed, and both short and long-term memory can be affected.

Causes

Human cells normally contain 23 pairs of chromosomes. Down syndrome occurs due to an abnormal cell division involving chromosome 21, resulting in an extra chromosome. There are three genetic variations that can cause Down syndrome:

1. Trisomy 21: About 95% of cases are due to Trisomy 21, where individuals have three copies of chromosome 21 in all cells.
2. Mosaic Down Syndrome: A rarer form, where some cells have an extra copy of chromosome 21, caused by abnormal cell division after fertilization.
3. Translocation Down Syndrome: Occurs when part of chromosome 21 becomes attached to another chromosome before or at conception.

Risk Factors

Certain factors increase the likelihood of having a child with Down syndrome:

• Maternal Age: The risk increases with advancing maternal age, particularly after 35.
• Genetic Translocation Carriers: Both parents can pass the translocation.
• Previous Child with Down Syndrome: Parents who have one child with Down syndrome have a higher risk of having another child with the condition.

Complications

People with Down syndrome may experience various complications, including:

• Heart Defects: Approximately half are born with congenital heart defects, which may require surgery.
• Gastrointestinal Issues: Abnormalities in the intestines, esophagus, trachea, and anus, along with an increased risk of digestive problems.
• Immune System Disorders: Higher risk of autoimmune disorders, certain cancers, and infections like pneumonia.
• Sleep Apnea: Due to airway obstruction from soft tissue and skeletal changes.
• Obesity: Greater tendency towards obesity.
• Spinal Problems: Risk of spinal cord injury from neck overextension.
• Leukemia: Increased risk in young children.
• Dementia: Increased risk, with symptoms potentially appearing around age 50.
• Other Health Issues: Endocrine problems, dental issues, seizures, ear infections, and hearing and vision problems.

Life Expectancy

The life expectancy for individuals with Down syndrome has significantly improved, with many living beyond 60 years, depending on the severity of their health issues.

Prevention and Genetic Counseling

There is no way to prevent Down syndrome. However, genetic counseling can help parents understand their risks and make informed decisions. Genetic counselors provide information on prenatal tests and discuss their pros and cons, helping parents prepare for the potential outcomes.

Conclusion

Down syndrome is a complex genetic disorder with a wide range of symptoms and health issues. Early intervention and supportive care can significantly enhance the quality of life for those affected, enabling them to lead fulfilling lives.

Sources

1. Mayo Clinic. (2022). Down syndrome. Retrieved from Mayo Clinic
2. National Down Syndrome Society. (2023). Down Syndrome Facts. Retrieved from NDSS
3. Centers for Disease Control and Prevention. (2021). Facts about Down Syndrome. Retrieved from CDC
4. Genetics Home Reference. (2022). Down syndrome. Retrieved from MedlinePlus