Down syndrome is a disorder where a child is born with an additional copy of the 21st chromosome. Children born with the condition may have physical as well as mental developmental delays and abnormalities. They may also be born with eye disorders and other anomalies, including dementia, heart disease and abnormalities involving the thyroid, intestines and skeleton.
Every child born with the disorder is unique, but many disabilities are lifelong and may shorten life expectancy. However, children with the condition can live healthy and fulfilling lives.
Also Known As
- 47, XX, +21
- 47, XY, +21
- Trisomy G
- Down's syndrome
There are three forms of Down syndrome, namely Mosaicism, Translocation and Trisomy 21.
- Mosaic Down syndrome manifests when an infant is born with an extra chromosome in only certain cells.
- Translocation Down syndrome occurs when a child has only an additional part of chromosome 21.
- In Trisomy 21, Down syndrome is the predominant type of the disease. All of the child's body cells have an extra chromosome 21 copy.
Causes & Risk Factors
Both parents pass their genes, which are carried in chromosomes, on to the child. Each child's cell is expected to obtain 23 chromosome pairs, for a total of 46 chromosomes. Half of the chromosomes belong to the mother and half to the father.
One of the chromosomes fails to differentiate correctly in children with Down syndrome. The infants get three copies or an additional partial chromosome 21 copy, instead of two. As the brain and physical features grow, the extra chromosome causes issues.
Down Syndrome is the most common genetic condition in the United States, affecting about 700 babies. Babies of women aged 35 and above have a greater probability of having Down syndrome. Other parents at a greater risk of having a child with the disorder include:
- Genetic translocation carriers
- People with a Down syndrome family history
Signs & Symptoms
Down syndrome babies typically have some characteristic signs at birth, including:
- Upward slanted eyes
- Eyes with oblique fissures
- Misalignment of eyes (strabismus)
- Epicanthic skin folds on the inner corner of the eyes
- Brushfield's spots - Tiny white spots on the colored portion of the eye (iris)
- Flat facial characteristics
- Abnormally shaped ears
- Deficient muscle tone
- Bulging tongue
- Short neck
- Small head and ears
A child with the syndrome may be born an average size but grows more slowly than a healthy baby.
There is generally a degree of developmental disorder in children with Down syndrome, but it is mostly mild to moderate. Delays in mental and social development can be a pointer that the child may have:
- Slow learning capabilities
- Poor judgment
- Impulsive behavior
- Short attention span
Medical complications that often accompany Down syndrome include:
- Poor vision
- Clouded eyes (cataracts)
- Interrupted breathing during sleep (sleep apnea)
- Late tooth growth, leading to chewing difficulties
- Thought and memory problems (dementia)
- Low thyroid function (hypothyroidism)
- Hip disorders, such as dislocations
- Congenital heart defects
- Chronic constipation
- Hearing loss
- Alzheimer's disease later in life
Often, people with Down syndrome are more vulnerable to infections, including eyes, skin, respiratory, and urinary tract infections.
Screening and diagnostic tests help to identify the syndrome during pregnancy. Screening for the disorder is recommended as a routine part of prenatal care for women over 35, fathers over 40, and people with Down syndrome family history. The tests can help to assess the chances of the fetus having the disease. There are various prenatal screening techniques, such as ultrasound evaluation and blood tests between 14 and 24 weeks of gestation. Screening tests are definitive, but they are safer for the mother and her developing baby.
If screening tests are indicative of Down syndrome, the doctor orders diagnostic tests for confirmation. Diagnostic tests include:
- Chorionic villus sampling
- Paralogue sequence quantification
- Fluorescence in situ hybridization (FISH)
- Percutaneous umbilical blood sampling (cordocentesis)
- Quantitative-fluorescent polymerase chain reaction (QF-PCR)
At birth, the doctor may also conduct a physical examination of the infant and order a blood test (karyotype) to confirm Down syndrome. The health care professional may refer the parents to a clinical geneticist for genetic testing and counseling.
Down syndrome is a lifelong disorder, and treatment is symptomatic. The management of the condition is multidisciplinary and depends on each patient's physical and mental needs and personal strengths and limitations. The patient is likely to need care from a health professional team, including an ophthalmologist, cardiologist, neurologist, child psychiatrist, developmental pediatrician, orthopedic specialist, pediatric pulmonologist, gastroenterologist, neurosurgeon, audiologist, physical and occupational therapist, speech and language therapist, etc.
Parental education is one of the critical aspects of Down Syndrome management. Parents need to be informed of the many potential problems associated with the disorder to be better diagnosed and treated.
Surgical intervention may be necessary for some eye disorders, such as strabismus.
Prognosis & Long-Term outlook
Down syndrome patients now live longer, happy and more productive lives than ever before. Recent medical advances, institutional and cultural support for the patients and their families offer remarkable opportunities to help surmount the challenges associated with the disorder. Today, Down syndrome patients have an average life expectancy of about 55 years.
Prevention & Follow Up
Down syndrome patients and their families need to build a strong support network and maintain a close relationship with experts who understand the disease's unique challenges.