Down syndrome (DS), or trisomy 21, is the most common genetic cause of developmental disabilities and mental retardation. It is caused by a baby getting extra genetic material from chromosome 21. It occurs in about 1 in 700 births, is more common in pregnancies with a mother over age 35, and it is more common in boys.
Although sometimes diagnosed prenatally because of an abnormal (low) serum alpha-fetoprotein or after an amniocentesis or chorionic-villus sampling is done in an at risk pregnancy with the finding of abnormal chromosomes, most children are diagnosed at birth because of typical clinical manifestations or findings. These include having poor muscle tone, a small head, flat nasal bridge, upward slanting eyes or palpebral fissures, epicanthal folds, small ears, small mouth, single palmer crease, short fifth finger that turns inward (clinodactyly), excess skin fold at the nape of the neck, large tongue, and a large space between the fourth and fifth toes.
Newborns may be suspected of having trisomy 21 if they have many of the above clinical findings, especially if they have a medical problem that is associated with this condition and for which they are at increased risk, including a 50% risk of congenital heart defects (atrioventricular canal, tetralogy of Fallot, ASDs, PDAs, VSDs) and a 12% risk of gastrointestinal problems (TE Fistula, duodenal atresia (a congenital blockage of the small intestines), or pyloric stenosis).
They are also at increased risk for hypothyroidism (a low thyroid hormone level), eye abnormalities (cataracts, strabismus, nystagmus, glaucoma and refractive errors), hearing loss and deafness (usually from repeated ear infections), mental retardation (ranging from mild (IQ 50-70), moderate (IQ 35-50), and sometimes severe (IQ 20-35), developmental delays (including speech and motor delays), leukemia (<1% risk), hip dislocation, constipation, obstructive sleep apnea, poor growth (special growth charts are available to plot your child's growth), dental abnormalities, atlantoaxial instability, obesity, seizures and very dry skin.
In the nursery, children who are suspected of having trisomy 21 will usually have an evaluation to make sure he doesn't have a heart problem. This will include an EKG, chest x-ray, and a cardiology consult with an echocardiogram. He will also have blood drawn to check his chromosomes to confirm the diagnosis and make sure he doesn't have a balanced translocation (which requires consultation with a genetics specialist to discuss the risk of having another baby with this condition). He will also have a blood screening test to check for hypothryoidism.
Problems that can occur in the newborn period include difficulty with feeding and poor growth, especially if he also has a heart problem. He may have to be on a concentrated, high calorie formula to help him gain weight. His initial visit during the newborn period will include a detailed evaluation of his growth and development, with special attention paid to look for eye abnormalities. It is also a good time to get a referral to a Down Syndrome specialty clinic or support group if one is available in your area and to an Early Child Intervention program for occupational and physical therapy.
During the first year of life, routine doctor visits will include the normal well child examinations and immunizations, but special attention will be paid to look for thyroid problems (blood tests will usually be done at 12 months), hearing loss or deafness (a referral to an audiologist for formal testing should be considered if there is any question of hearing loss), eye abnormalities (a referral to an ophthalmologist at 9 months is usually indicated), and problems with feeding or growth.
In early childhood (ages 1-5 years), your pediatrician will continue to monitor your child's growth and development, including yearly testing to look for thyroid problems, and possibly x-rays of the cervical spine to look for atlantoaxial instability or subluxation, especially if your child is going to be active in contact sports or Special Olympics. He should also have an early visit to a pediatric dentist to monitor for any dental abnormalities.
In late childhood (ages 5-13 years) and adolescence to early adulthood (ages 13-21 years), your pediatrician will continue to monitor your child's growth and development, including yearly testing to look for thyroid problems, regular screening of his vision and hearing, and he may discuss any learning or behavioral problems your child may be having. In older children, it may be necessary to discuss vocational planning, or placement in a group home or workshop.
You should also have discussions about puberty and sexual development with your older child and the risk of having a child with trisomy 21.
The American Academy of Pediatrics has published a policy statement on the Health Supervision for Children With Down Syndrome that should be helpful for Pediatricians and parents of children with down syndrome. It includes a list of growth charts for children with down sydnrome so that you can more accurately monitor your child's growth.
Recommended Reading List:
In association with amazon.com, these books can help you to learn more and become better educated about your child's condition, its treatment and preventing complications.