diease

Down's Syndrome


OVERVIEW OF Down's Syndrome :

Down syndrome (sometimes called Down’s syndrome) is a condition in which a child is born with an extra copy of their 21st chromosome — hence its other name, trisomy 21. This causes physical and mental developmental delays and disabilities.


CAUSES :

Chromosomes are small packages of genes in the body. They determine how a baby’s forms and functions as it grows during pregnancy and after birth. A baby is form with 46 chromosomes.

Babies with Down’s syndrome have an extra copy of one of these chromosomes, chromosomes 21.

The chromosome having extra copy of chromosome is termed as Trisomy. Down’s syndrome is also known as Trisomy 21.  This extra copy changes how the baby’s body and brain develop which can cause both mental and physical challenges for the baby.

Inspite the people with Down syndrome might act and look similar each person tends to show different abilities. People with Down syndrome usually have an IQ ( a measure for intelligence) in the mild to moderately low range and are slower to speak than other children.

Some common physical features of Down syndrome include:

  • A flattened face, especially the bridge of the nose
  • Almond-shaped eyes that slant up
  • A short neck
  • Small ears
  • A tongue that tends to stick out of the mouth
  • Tiny white spots on the iris (colored part) of the eye
  • Small hands and feet
  • A single line across the palm of the hand (palmar crease)
  • Small pinky fingers that sometimes curve toward the thumb
  • Poor muscle tone or loose joints
  • Shorter in height as children and adults

 

There are three types of Down syndrome. People often can’t tell the difference between each type without looking at the chromosomes because the physical features and behaviors are similar.

 

Trisomy 21: 

About 90-95% of people with Down syndrome shows Trisomy 21. With this type of Down syndrome, each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies.

Translocation Down syndrome: 

This type accounts for a small percentage of people with Down syndrome (about 3%). This occurs when an extra part or a whole extra chromosome 21 is present, but it is attached or “trans-located” to a different chromosome rather than being a separate chromosome 21.

Mosaic Down syndrome: 

This type affects about 2% of the people with Down syndrome.2Mosaic means mixture or combination. For children with mosaic Down syndrome, some of their cells have 3 copies of chromosome 21, but other cells have the typical two copies of chromosome 21. Children with mosaic Down syndrome may have the same features as other children with Down syndrome. However, they may have fewer features of the condition due to the presence of some (or many) cells with a typical number of chromosomes.

 


COMMON CLINICAL SIGNS AND SYMPTOMS :

Symptoms:

 Small chin

Slanted eyes

Poor muscle tone

 Flat nasal bridge

Single crease of palm

Protruding tongue due to small sized chain

Obstructive sleep apnoea

Big toe

Hip dislocations

Obesity

spasms

The other symptoms include:

Neurological:

Many milestone development are getting disturbed. For example an ability to crawl which is occurring around 5 months might takes 8 months to develop.

And walking at 14 months of age is the normal. But the child with downs syndrome tends to walk at 21 months.

Most of the individuals show the IQ level- 50 to 69 which is mild

Moderate- 35 to 50

Intellectual disability – 20-35

In mosaic down syndrome the IQ score is 10-30%.

 

Senses:

Brushfield ( small white or grayish spots on the outer part of the iris)spots appear. Between 20-50 % of the population has Strabismus in which there in un coordination of two eye balls. Keratoconus which is termed as thin cone shaped cornea and glaucoma increase in the eye pressure are also more common.

Otitis median with effusion is seen in 50-70 and chronic ear infections occurs in 40-60% of the cases.

Poor eustachian tube function.

Excessive ear wax can also cause hearing loss due to obstruction of the outer ear canal.

Heart:

The congenital heart disease is 40%. Of those 80% has an atrioventricular septal defect or ventricular septl defect. Mitral valve prolapse is also common as age progresses.

Tetralogy of Fallot, Patent ductus arteriosus and hardening of the arteries is also common.

Cancer:

Acute lymphoblastic leukaemia and acute megakaryoblastic leukaemia is increased ehile the risk of other non blood cancer is decreased.

Leukaemia is more common among the down’s syndrome patients.

 

 Endocrine:

Thyroid gland problems occur in 20-50% of the individuals with the down’s syndrome. Type 1 diabetes mellitus is more common. Thyroid functions can be due to poorly or improper functioning of the thyroid gland.

Gastrointestinal:

Constipation is common among the people with the downs syndrome. One fatal condition called Hirschsprung’s disease occurs in 2-15% of the patient which is due to the lack of nerve cells controlling the colon.

 

Teeth

People with Down syndrome tend to be more susceptible to gingivitis as well as early, severe periodontal disease, necrotizing ulcerative gingivitis and early tooth loss, especially in the lower front teeth. 

People with Down syndrome also tend to have a more alkaline saliva resulting in a greater resistance to tooth decay despite decreased quantities of saliva,less effective oral hygiene habits, and higher plaque indexes.

Higher rates of tooth wear and bruxism are also common. Other common oral manifestations of Down syndrome include enlarged hypotonic tongue, crusted and hypotonic lips, mouth breathing narrow palate with crowded teeth, class III malocclusion with an underdeveloped maxilla and posterior crossbite, delayed exfoliation of baby teeth and delayed eruption of adult teeth, shorter roots on teeth, and often missing and malformed (usually smaller) teeth. Less common manifestations include cleft lip and palate and enamel hypocalcification. (20% prevalence).

Taurodontism an elongation of the pulp chamber, has a high prevalence in people with DS.

Fertility:

Males shows sterility problems when compared to females. Menopause tends to occurs at an earlier age. The  sperm development is interfered  in Down’s syndrome.

 


DIAGNOSTIC :

Screening tests:

It checks whether the mother is carrying a baby with down syndrome. But this test cannot detect whether the baby is suffering from the disease.

Diagnostic test:

It can identify or diagnose whether the baby has down syndrome.

Screening test during pregnancy:

It is the routine part of the prenatal care. The screening test can only identify the risk of carrying the baby with Downs syndrome, they can help to rule more about the specific diagnostic test. It can be used in first trimester .

The first trimester combined test, which is done in two steps, includes:

  • Blood test. This blood test measures the levels of pregnancy-associated plasma protein-A (PAPP-A) and the pregnancy hormone known as human chorionic gonadotropin (HCG). Abnormal levels of PAPP-A and HCG may indicate a problem with the baby.
  • Nuchal translucency test. During this test, an ultrasound is used to measure a specific area on the back of your baby's neck. This is known as a nuchal translucency screening test. When abnormalities are present, more fluid than usual tends to collect in this neck tissue.

Integrated screening test

The integrated screening test is done in two parts during the first and second trimesters of pregnancy. This test reveals the risk for the disease.

First trimester:

Part one includes a blood test to measure PAPP-A and an ultrasound to measure nuchal translucency.

Second trimester:

The quad screen measures your blood level of four pregnancy-associated substances: alpha fetoprotein, estriol, HCG and inhibin A.

Diagnostic tests that can identify Down syndrome include:

Chorionic villus sampling(CVS):

The cells are derived from the placenta and it is used to analyse the fetal chromosome. The test is typically performed between 10 and 13 weeks of pregnancy. The risk of getting aborted is very much low in patient with the CVS.

Amniocentesis:

A sample of the amniotic fluid surrounding the fetus is withdrawn through a needle inserted into the mother's uterus. This sample is then used to analyze the chromosomes of the fetus. Doctors usually perform this test in the second trimester, after 15 weeks of pregnancy. This test also carries a very low risk of miscarriage.

Chromosomal karyotyping:

Using the blood sample trisomy can be identified.

 


TREATMENT AND PROGNOSIS :

Half of the Down’s syndrome shows congenital cardiac defects and it can be corrected by Paediatric cardiologist.

Applied Behavioural analysis including  positive behavioural approach:

Includes training the parents ,teachers, school faculties and other peer group of the child affected with this disease.

Cognitive behavioural therapy:it includes the stress management in the children and also relieve them from their anxiety and obsessive repetative behaviours.This therapy also focuses on the child’s emotional disturbances.

Medications: They are indicated mainly to treat the major depressive disorder and anxiety disorder.

Occupational or physical therapy: They mainly indulge in sensory processing and motor coordination behaviour of the child.

Social communication therapy: It includes the speech therapy to help pragamatics


PREVENTION :

Prenatal screening is must in diagnosis the disease.

Check for the familial history, if present be cautious.

Prognosis:

The life expectancy can be achieved at an higher rate for the down’s syndrome individuals.