Down syndrome Overview
What is Down syndrome?
Down syndrome is a genetic disorder that has several unique features. By far it’s the commonest chromosomal disorder among humans. Chromosomes are protein and DNA combinations stored inside the nucleus of the cells. They contain genes (special DNA fragments) that are responsible for your appearance, traits, body functions, and even for your behavior.
A normal human has 23 pairs of chromosomes. They are named from one to twenty three according to their characteristics. Each and every chromosome is vital for body functions. In this disease, the 21st chromosome pair has been replaced by 3 chromosomes. This is why the it is called as Trisomy 21 among the medical professionals.
“Too much of anything is bad” isn’t it? Unfortunately, regarding chromosomes, even just an additional chromosome is bad.
Signs and symptoms of Down syndrome
Most of the features of this disease are present from the time of birth. But, they may not be very evident. As the baby grows up, the symptoms become prominent.
The commonest features of Down syndrome are listed below.
- Flat occiput and flat face
- Flat nasal bridge
- Brushfield’s spots – Tiny black dots on the iris of the eyes
- Hypertelorism – Wide spaced eyes
- Small, low set of ears – The ears are at a lower level comparatively to the eyes
- Small mouth
- Protruding tongue – The tongue may appear large since it protrude through a small mouth
- Short neck
- Single simian crease – Only one transverse palmar crease
- Short fingers with clinodactyly – an abnormally curved little finger
Complications of Down syndrome
Even if the 21st chromosome triple are structurally normal, Down syndrome invariably leads to many complications. Some of them are evident at the time of birth. Some manifest as the child becomes older.
- 50% of the Down syndrome babies are born with congenital heart defects including holes between atria (ASD) or ventricles (VSD), tetralogy of fallot, etc.
- Any gastrointestinal malformation can occur, starting from mouth till the anus.
- Visual and hearing impairment may appear as the child gets older.
- Learning and intellectual disabilities occur in almost all the children.
- Abnormal immune responses may cause autoimmune disorders, a condition where the immune system attacks the own body cells.
- Diseases due to hormonal imbalances including diabetes mellitus, malignancies like leukemia and memory disorders like dementia may manifest during the adult life.
Cause or risk factors for Down syndrome
Advanced maternal age, especially if the mother is over 35 years of age, is a well-known risk factor than can cause Down syndrome of the baby. Inherited forms of Down syndrome are rare, yet it can happen if the mother or father contains 21:21 chromosomal translocation. Those parents carry a 100% risk of having Down syndromic babies in their subsequent pregnancies. Therefore, those who have a child with Down syndrome should ideally undergo genetic evaluation before the next pregnancy.
Diagnosis of Down syndrome
Down syndrome is suspected when a child is born with above mentioned signs and symptoms. However, having one or several features do not necessarily indicate Down syndrome. In-fact, the child may be perfectly normal. That’s why laboratory confirmation is essential. Cytogenetic studies including Karyotyping and fluorescence in situ hybridization (FISH) are the best genetic tests, the latter even being better, for the diagnosis.
Treatment and management
Each and every baby suspected of having this syndrome should undergo ultrasound scan of the heart to exclude any heart defect.
As the child grows older following investigations may be necessary to exclude or diagnose any secondary complications.
- Ophthalmic (eye) investigations
- Thyroid function tests
- Metabolic screening
- Auditory brainstem response
- Bone marrow examination to rule out leukemia
Life expectancy
Due to the advancement of the medical technology, the survival of Down syndrome people has been dramatically improved over the last forty years. Currently, a Down syndrome adult is expected to live beyond the age of 60 years. However, a baby born with this syndrome has a 25% probability to die during the 1st year of life. If he survives the 1st year of life, median life expectancy rises up to 50 years. Continuous medical investigations and monitoring, on-time medical or surgical interventions, and a good family support and care is essential for the optimal survival.
Down Syndrome Prevention
Unfortunately there are no medical or surgical interventions to prevent the Down syndrome. WHO emphasize on avoiding pregnancies after the maternal age of 35 years as it carries a risk of Down syndrome. Intra-uterine diagnostic tests by amniocentesis are offered in some countries for the high risk mothers. If the fetus is diagnosed to have Downs, Abortion is a way of prevention. However, ethically it’s controversial.
