Down Syndrome

What is Down Syndrome?

Down syndrome, also called Down’s syndrome, is a genetic condition due to which a child’s mental and physical development gets delayed.

What Causes Down Syndrome?

Down syndrome occurs when instead of the normal 46 chromosomes that a child inherits from his parents during conception, he gets an extra copy of chromosome 21, thus having 47 chromosomes that account for the various disabilities.

This syndrome, named after the English physician John Langdon Down, can be classified into 3 types on the basis of the abnormalities of the chromosomes.

Types

• Trisomy 21, where there are three copies of the chromosome 21 rather than the habitual two. Also called Trisomy G, it accounts for about 95% of all Down’s syndromes.
• Mosaicism, where some cells have 46 chromosomes while some have 47, with an extra copy of chromosome 21. Also known as Mosaic Down’s Syndrome, this condition accounts for approximately 2% of Down syndrome cases.
• Translocation, where a part of the chromosome 21 gets attached (translocated) to another chromosome, usually the chromosome 14. This is said to affect 2?3% of cases of Down syndrome patients.

Is Down Syndrome Genetic/Hereditary

All cases are genetic, but Trisomy 21 and mosaicism Down syndrome are not inherited. However, about one-third of children having the translocation variety inherit the condition from their parents.

Risk Factors

• Advanced age of mother: The tendency of chromosomes to divide incorrectly increases with a woman’s age and consequently places them at a higher risk of conceiving a baby with Down syndrome. A 35 years old woman carries a risk of about 1 in 350 whereas a 40 years old woman carries a risk of about 1 in 100 of bearing a child with the disorder.
• Mother has had a child with Down’s syndrome: If a woman already has had a baby with Down syndrome, then she has about a 1 in 100 chance of conceiving another baby with the condition.
• Having a family history of the condition

Signs and Symptoms

Physical Characteristics

• Flattened features of the face
• A poorly formed nasal bone and a flat nasal bridge
• Small head
• Short neck
• A small mouth with a protruding tongue
• Eyes having a tendency to slant upward
• Oddly shaped or small ears
• A reduced muscle tone suggesting hypotonia
• Small and broad hands with relatively small fingers and a palm having a single crease
• Small feet
• The colored portion of the eye, called Iris having tiny, white spots called brushfield spots
• Oral manifestations involving absent primary and permanent teeth, a small mouth with a protruding tongue and reduced salivary flow
• A big space (sandal sap) between the first and second toe
• Short height

Why do People with Down Syndrome Look Alike

Many people with Down syndrome look alike, with similar physical features like short height or almond shaped eyes, as they often have similar genetic structure with an extra copy of chromosome 21. However, all do not look the same and they also share physical characteristics with their own families.

Neurological Symptoms

• Delay in motor development such as sitting up, crawling, walking, reaching or talking
• Delay in speech and attainment of self-care skills like eating, getting dressed or knowing toilet rules
• Limited attention span
• Behavioral problems involving poor judgment, impulsiveness, hyperactivity
• Learning disability
• Seizures
• Extensive flexibility

Complications

• Congenital heart defects
• Pulmonary hypertension that can lead to lung damage
• Hearing disability
• Ocular problems such as near or farsightedness, strabismus (cross-eyed), cataract, nystagmus, keratoconus and glaucoma
• Breathing problems such as sleep apnea and asthma
• Thyroid problems like hypothyroidism
• Digestive problems such as common constipation, diarrhea, indigestion and even the serious ones like small bowel obstruction, coeliac disease, reflux and Hirschsprung disease
• Infections such as pneumonia
• Childhood leukemia
• Unstable upper spine
• Cervical spine abnormalities such as Atlantoaxial instability
• ADHD
• Autism spectrum disorder (ASD)
• Dementia
• Obesity

How is Down Syndrome Diagnosed?

Prenatal screening tests that consider the risk if a baby has the syndrome or not are followed by diagnostic tests that may confirm if he will have the condition after birth.

Screening Tests during Pregnancy

First Trimester Combined Test

This test, done between 11-14 weeks of pregnancy involves:

1. Blood test to measure the levels of pregnancy-associated plasma protein A (PAPP-A) and the pregnancy hormone called beta-HCG (human chorionic gonadotropin) since abnormal levels of both may indicate a problem with the baby.
2. Nuchal translucency ultrasound screening test to check the collection of fluid at the back of the baby’s neck, since a greater amount of fluid than usual indicates the presence of some abnormality.

Triple Screen or Quadruple Screen Test

Also known as the multiple marker test, this is carried out between 15 and 18 weeks of pregnancy and measures the amount of normal substances in the mother’s blood.

Integrated Screening Test

Done in two parts, the first and second trimester quadruple screen uses the combined results to present a probable outcome of the condition.

Cell-Free Fetal DNA Analysis

Usually done after 10 weeks of gestation (in high risk cases), this looks for fetal DNA circulating in the mother’s blood, giving more specific results.

Diagnostic Tests during Pregnancy

Amniocentesis

This, normally done after 15 weeks of pregnancy analyzes the chromosomes of the fetus by using a sample of its amniotic fluid and contains a slight risk of miscarriage.

CVS (Chorionic Villus Sampling)

Carried out between 10 and 12 weeks of pregnancy, it checks the fetal chromosomes by taking cells from the placenta and carries a higher miscarriage risk.

Cordocentesis

Also called percutaneous umbilical blood sampling and generally performed after 18 weeks, this test examines chromosomal defects with the help of fetal blood taken from a vein in the umbilical cord and contains a greater miscarriage risk than both amniocentesis and CVS.

Tests after Birth

After the baby is born, a physical examination is carried out to look for the characteristic symptoms. If results positive, a blood test called karyotype might be done to analyze his chromosomes and confirm the syndrome.

Treatment and Management

Early Intervention Programs

Since children having this syndrome develop slowly as compared to normal kids, special programs by therapists may provide affected children with an early stimulation so that they improve their quality of life.

• A speech and language therapist may help in improving his language skills
• A pediatric physiotherapist may aid him in developing his motor skills
• A pediatric neurologist may provide support in improving his cognitive skills

Educational Strategies

Special educational procedures like integrated classrooms may also aid an affected child in learning life skills.

Feeding Strategies

Due to poor muscle tone and protruding tongue, generally all babies with the condition are messy eaters and most of the ways of food intake such as breastfeeding or bottle feeding usually take a longer time than normal babies. At times, some children face feeding problems like difficulty swallowing, requiring to be fed with the help of a special tube, called a gastronomy tube or a G-tube, inserted through the abdomen to directly deliver the necessary nutrition.

Medication

Several studies put forward the view that administration of amino acids such as Acetyl-L-Carnitine and L-Carnosine in the form of tablets may nourish brain cells, thereby helping in Down’s syndrome. However, more research needs to be done in this area.

Management of the Associated Conditions

Dietary Therapy

According to certain studies, an addition of vitamins and minerals to the diet may help in dealing with certain complications of the disorder. B12 seems to normalize metabolism; vitamin C may provide protection against the occurrence of Alzheimer’s disease, and the mineral zinc may improve subclinical hypothyroidism associated with the condition.

Surgery

Surgical treatment is provided to overcome cardiac and GI anomalies that may emerge with the condition, and generally, careful anesthetic measures are undertaken during the preoperative period since children affected with the condition tend to be hyperactive and hard to manage.

Immunization

Immunization can be given to prevent the occurrence of infections such as hepatitis B.

Can Down Syndrome be Prevented

Although there are no known ways to prevent the syndrome, genetic counseling before conceiving may help in understanding the chances of having a baby with the syndrome.

Prognosis

Prognosis of Down’s syndrome that is based on the nature and severity of the associated complications has improved over the years.

Life Expectancy: How Long do People with Down Syndrome Live

With modern medical assistance, children having the condition usually have a long life expectancy with nearly 80% living up to age 55 and even longer. According to a survey, Joe Sanderson, 80, from Saltburn, Cleveland, is the oldest living person with Down syndrome.

Can People with Down Syndrome Reproduce

Reproduction is a rare phenomenon with people affected with Down syndrome and they need careful and sensitive advice regarding the issue of having children.

Prevalence and Incidence Statistics: How Common is it

Considered to be the most common chromosomal disorder, there are about 6000 diagnoses every year, with around one in every 700 babies being born with Down’s syndrome. According to several studies, the survival rate of African American infants having the syndrome is much lower as compared to white babies. However, more research needs to be done to decipher the reason of this disparity.

Down Syndrome vs. Autism

Various studies have been carried out to compare the prognosis and quality of life for adults living with Down syndrome and those with autism spectrum disorders. Although the conditions may often coexist, it has been suggested by experts that Down syndrome patients have better social and residential independence, with more frequent contact with family and friends, better educational capabilities and less behavioral problems than those with ASD.

Down syndrome ICD 9?CM and ICD?10 CM Codes

The ICD-9-CM code for the syndrome is 758.0, and the ICD-10-CM code is Q90.

References:

1. http://www.mayoclinic.org
2. http://kidshealth.org
3. http://www.ndss.org
4. http://www.nhs.uk
5. http://www.healthline.com
6. http://patient.info