Down syndrome

General: The severity and specific type of symptoms vary significantly among patients. Patients are generally born with distinct physical characteristics, as well as mental disabilities that range from mild to severe.

Facial characteristics: Individuals with Down syndrome have distinct facial characteristics. Some of the most common traits include a protruding tongue, small head, flattened facial features, eyes that slant upward, small and low-set ears, irregularly shaped mouth, narrow and high palate, pushed in nasal bridge, and irregular or crooked teeth (that often develop later than normal). Patients may also develop Brushfield's spots, which are buildups of tissue in the colored part of the eyes that do not affect vision.

Other physical characteristics: Infants with Down syndrome may be average size shortly after birth. However, they typically grow more slowly and remain smaller than other children who are of similar age. Other common symptoms include poor muscle tone, short fingers, broad and short hands that have single creases in the palms, and excessively flexible joints.

Intellectual symptoms: Children with Down syndrome also have some degree of intellectual disabilities, which range from mild to severe. Researchers typically use intelligence quotient (IQ) tests to measure the severity of a person's intellectual disabilities. Individuals who have 85-115 IQs are considered to have average intelligence.

Patients with mild intellectual disabilities have IQs of 52-69. From birth to age six, patients are able to develop normal social and communication skills, but motor coordination is slightly impaired. By late adolescence, patients are able to learn until about a sixth-grade level. They are generally able to learn appropriate social skills. Adults with mild intellectual disabilities are usually able to work and support themselves, although some patients may need help during times of social or financial stress.

Patients with moderate intellectual disabilities have IQs of 36-51. Children younger than six years old are able to talk or communicate with others, but social awareness is generally poor. Motor coordination is typically fair. Adolescents are able to learn some occupational and social skills. For instance, they may be able to learn how to travel alone in familiar places. Adults may be able to support themselves with a job. They usually require guidance and assistance during mild social or financial stress.

Patients with severe intellectual disabilities have IQs of 20-35. Young children can say a few words, but their speech is limited. Motor coordination is generally poor. Adolescents can usually talk or communicate with others. They are able to learn simple habits. Adults typically require lifelong assistance and guidance with daily activities.

Patients with profound intellectual disabilities have IQs of 19 or lower. Children younger than six years old have very little motor coordination and may require nursing care. Adolescents typically have limited motor and communication skills. Adults usually require lifelong nursing care.

Behavioral characteristics: Common behavioral characteristics associated with Down syndrome include cheerfulness, spontaneity, gentleness, patience, and tolerance. Some patients may have anxious or stubborn personalities.

General: In the past, prenatal screening for Down syndrome was offered to older mothers who were at high risk of having a baby with the disorder. Today, the American College of Obstetricians and Gynecologists recommends offering Down syndrome screening as part of prenatal testing for pregnant women of all ages. If screening tests indicate that a mother is at high risk of having a baby with Down syndrome, prenatal diagnostic tests may be performed. However, because diagnostic tests may lead to complications during pregnancy, pregnant mothers should discuss the potential risks and benefits of screening before making any decisions.

Screening tests during pregnancy :

There are many tests that can be performed during pregnancy to determine if a mother has a high risk of having a baby with Down syndrome. The most effective screening includes an ultrasound and blood tests, which are performed between the 11th and 14th week of pregnancy. These tests can help determine if a mother is at risk of having a baby with Down syndrome, spina bifida (a condition that occurs when the tissues surrounding the spinal cord do not develop properly), or other types of chromosomal disorders. These tests only indicate if there is a risk of Down syndrome. They cannot diagnose the disorder. Some women may be at risk of having babies with Down syndrome but give birth to healthy babies.

Ultrasound: During an ultrasound, a wand-like device is rubbed against the mother's stomach. Ultrasounds use high-energy sound waves (ultrasound) that bounce off internal tissues or organs to produce images of the fetus. During the ultrasound, a doctor performs a test, called the nuchal translucency screening test. The doctor measures the clear (translucent) space in the tissue at the back of the fetus' neck. The fetus may be at risk of having Down syndrome if the clear space is larger than normal. This is because fluid often collects inside this tissue if abnormalities are present.

Blood tests: Blood tests are also performed in combination with an ultrasound. Blood tests measure the amount of pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (HCG). If the mother has low levels of PAPP-A and HCG, it may suggest a problem with the baby.

If these tests indicate that there is a risk of Down syndrome, diagnostic tests, such as amniocentesis or chorionic villus sampling, may be recommended. These diagnostic tests can definitively determine if the fetus has Down syndrome.

Diagnostic tests during pregnancy :

Individuals at high risk of having of having babies with Down syndrome may choose to undergo diagnostic tests during pregnancy. Each of these tests can diagnose Down syndrome with 98-99% accuracy. However, there are serious risks associated with these tests.

Amniocentesis: During amniocentesis, a long, thin needle is inserted into the abdominal wall to the uterus and a small amount of amniotic fluid is removed from the sac surrounding the fetus. The fluid is then analyzed for an extra chromosome 21. This test is performed after 15 weeks of gestation. The risk of miscarriage ranges from one out of 200-400 patients. Some patients may experience minor complications, such as cramping, leaking fluid, or irritation where the needle was inserted.

Chorionic villus sampling (CVS): During chorionic villus sampling (CVS), a small piece of tissue (chorionic villi) is removed from the placenta during early pregnancy. Depending on where the placenta is located, CVS can be performed through the cervix (transcervical) or through the abdomen (transabdominal). The tissue sample is then analyzed for the presence of an extra chromosome 21. This procedure may be performed between the ninth and 14th week of gestation. The risks of infection or fetal damage are slightly higher than the risks of amniocentesis. Miscarriage occurs in about two percent of women who undergo this procedure.

Percutaneous umbilical blood sampling (PUBS): Percutaneous umbilical blood sampling (PUBS) may also be performed. During the procedure, a small sample of blood is taken from a vein in the umbilical cord. The sample is then analyzed for the presence of an extra chromosome 21. This test is usually performed after 18 weeks of gestation. This test poses a greater risk of miscarriage than both amniocentesis and CVS. It is usually only performed when a prompt diagnosis is needed.

Diagnostic tests for newborns :

After birth, Down syndrome may be diagnosed based on the infant's physical appearance. In order to confirm a diagnosis, a doctor usually orders a chromosomal karyotype test, which provides a picture of the person's chromosomes. A sample of the patient's blood is taken and analyzed for the presence of an extra chromosome 21.

General: Patients should regularly visit their doctors in order to treat and help prevent complications of Down syndrome. Patients typically live to be 50 years of age or older, depending on the severity of health-related problems.

Heart defects: About 50% of Down syndrome patients are born with heart defects, which range from mild to life-threatening. Some infants may need to undergo surgery to correct structural problems of the heart. Some of the most common heart abnormalities include endocardial cushion defect, ventricular septal defect, secundum arterial septal defect, tetralogy of Fallot, and isolated patent arteriosus. These defects occur when parts of the heart, such as the walls, chambers, or valves, do not develop properly.

Leukemia: Down syndrome patients are born with impaired cellular immunity. Therefore, children with Down syndrome have an increased risk of developing a type of cancer called leukemia. Researchers estimate that children and adolescents with Down are 10-30% more likely to develop leukemia than the general population.

Infectious diseases: Patients with Down syndrome generally have abnormal immune systems, making them more susceptible to infections and diseases. Pneumonia is one of the most common infections to affect Down syndrome patients.

Dementia: Adults with Down syndrome are more likely to develop dementia than people who do not have the syndrome. Dementia symptoms often develop before the age of 40. Dementia is the loss of mental ability that is so severe that it interferes with daily functioning.

Other problems: Down syndrome has also been associated with many other health problems, including gastrointestinal blockage, thyroid problems, hearing loss, dental problems, and poor vision.

General: Although Down syndrome is considered a genetic disease, most cases are not inherited. Instead, the disorder is usually caused by a spontaneous mutation, or mistake, during the development of the egg, sperm, or embryo.

In healthy individuals, cells contain 23 pairs of chromosomes. These chromosomes contain the building blocks of life called DNA (deoxyribonucleic acid). Each pair of chromosomes contains one chromosome from each parent. A patient with Down syndrome has an extra 21st chromosome. There are three possible ways this can happen.

Trisomy 21: More than 90% of Down syndrome cases are caused by trisomy 21. This happens when a sperm or egg cell does not divide properly. As a result, the child is born with three copies of chromosome 21, instead of just two.

Translocation Down syndrome: In about four percent of cases, Down syndrome develops when a copy of chromosome 21 attaches, or translocates, onto another chromosome. This can happen before or during conception. Individuals with translocation have two normal copies of chromosomes 21 and a third copy that is translocated.

This is the only type of Down syndrome that can be inherited, or passed down from parents to their children. When it is inherited, a mother or father does not have extra chromosomes. Instead, the chromosomes are arranged abnormally. However, the parent's sperm or egg cells will contain the translocated chromosome as well as a normal chromosome 21. When these two chromosomes (one normal and one translocated) combine with the other parent's egg or sperm to form an embryo, a total of three chromosome 21 are present.

Although a parent can pass the condition onto his/her children, the parent does not experience symptoms of Down syndrome. Only about 50% of translocation Down syndrome cases are inherited. The other half occur spontaneously.

Mosaic Down syndrome: In rare cases, only some of a person's cells have extra copies of chromosome 21. This condition, called mosaic Down syndrome, is usually the result of abnormal cell division after fertilization. Patients with mosaic Down syndrome tend to have higher intellectual quotients (IQs) than people with other types of Down syndrome.

Maternal age: As women age, there is a greater chance that the cells in her eggs will not divide properly. This increases the risk of having a child with Down syndrome. Women who are 35 years old have a one out of 385 chance that their children will have Down syndrome. Forty-year-old women have a one out of 106 chance of giving birth to children with Down syndrome. By age 45, the risk increases to one out of 30.

Mothers of Down syndrome children: In general, a woman who has one child with Down syndrome has a one percent chance of having another child with the condition.

Genetic carriers: Carriers of rearranged chromosome 21 may pass translocation Down syndrome onto their children. The risk of passing the translocation onto a child depends on the parent's gender. Fathers who carry the translocated chromosome have a three percent risk of having children with Down syndrome. Mothers who carry the translocated chromosome have a 12% chance of having children with Down syndrome.