Down Syndrome

Down Syndrome: Beyond the facial features

This is a fact-first primer on Down Syndrome. It aims to inform, and sensitise caregivers, peers and all readers about what this condition looks like, means medically, and the developmental differences it comes with. TSC will keep adding sections to this post to aid a complete and compassionate understanding of people born with an extra copy of chromosome 21.

What is Down Syndrome?

Down Syndrome is the most common chromosome-related genetic condition caused by the presence of three copies of Chromosome 21 instead of two. The extra genetic material — 47 chromosomes instead of 46 — results in cellular modifications that lead to changes in physical features, causes developmental delays, intellectual disability (mild to moderate), and a mix of health complications. 

Down Syndrome is not a disease. It can’t be prevented, or “cured”. It is a condition and its complexities can be managed well with support from your local paediatrician, and community of fellow parents.

The symptoms can manifest in varying degrees of intensity. Some individuals living the extra chromosome life can need a lot of medical attention, while others get by healthily. In fact, the life expectancy of individuals with Down Syndrome has gone up from 10 years in the 1960s to 60 years now; some individuals are known to have lived till the age of 80 years.

Globally, Down Syndrome presents itself in 1 in every 1,000-odd live births. In India, this number is ~1 out of 830 live births, or 32,000 new cases annually.

While some studies continue to contend that older mothers have a higher chance of having children with Down Syndrome, the medical and scientific jury is out on this one.

Understanding Down Syndrome

Down Syndrome results in a distinct facial and physical appearance, and a lower-than-typical IQ or intellectual disability (IQ<70) ranging from mild to moderate. At birth, children with Down Syndrome are smaller than others of the same gestational age. They also hit their developmental milestones later than their chronological peers, which means they will learn to talk, crawl, walk, but at a slower pace. Similarly, their intellectual development is also delayed.

Physical characteristics of a person with Down Syndrome:

  • A flattened face
  • Almond-shaped eyes that slant up, or are misaligned
  • Short neck with extra folds of skin on the back
  • Small ears
  • Palate malformation
  • Protruding tongue
  • White spots on the iris
  • Small hands and feet
  • Single line across the palm of the hand
  • Poor muscle tone (hypotonia), loose joints
  • Shorter height as compared to other children and adults of their chronological age

All persons with Down Syndrome may seem to look and act similar, but each person has a distinct personality, a full range of emotions and a unique set of abilities. Early intervention and therapy help kids work on areas of deficiency and reach their full potebtial. It is therefore important to never compare kids with Trisomy-21.

Types of Down Syndrome

Caused by a random rearrangement of genetic material, Down Syndrome has three sub-types depending on how the cells divide during conception. It cannot be passed down genetically, and there are many cases of persons with Down Syndrome having children with no anomalies.

1) Trisomy 21 is the most common type of Down Syndrome accounting for 95% of all cases in which a person has three copies of chromosome 21, instead of the usual two copies, in all cells.

2) Mosaic Down Syndrome presents in about 2% of all cases, and is extremely rare. Some of their cells have 3 copies of chromosome 21, while the others are normal with the typical two copies making it a “mix”. Children with this cell pattern have the same features as other kids with Down Syndrome, but the number of features are fewer.

3) In Translocation Down Syndrome an extra full copy, or part of chromosome 21 attaches itself to another chromosome instead of being a separate chromosome 21. It is rare — accounting for about 3% of all cases [3]. It is the only form of Down Syndrome that may be inherited from a parent [4].

Commonly Co-occurring Health Problems

The life expectancy of children with Down Syndrome has increased exponentially over the last few decades — from an average of 10 years in the 1960s to 60 years now — because of advancements in medical science, better access to sound information and resources. However, routine medical check-ups are extremely important as individuals may not be able to communicate their distress well causing a delay in diagnosis.

The most common medical problems [1] are:

  • Congenital heart defects
  • Sleep apnoea, other breathing difficulties
  • Periodontal diseases
  • Pronounced impact on the eyes leading to weak vision
  • Higher propensity to develop eye diseases like cataract, and earlier than the average population
  • Inner ear problems resulting in infections and hearing loss (partial or full)
  • Stomach and intestinal problems, including celiac disease
  • Underactive thyroid leading to hyper or hypothyroidism
  • Spinal problems such as spinal cord compression
  • Higher risk developing Alzheimer’s or dementia, with possible early onset
  • Immune disorders making them prone to cancers such as leukaemia 
  • Obesity
  • Diabetes mellitus
  • Mental health issues, including conduct disorder, depression, anxiety [6]
  • Early menopause
  • Xerodermatitis (dry skin)
  • Seizures
  • High cholesterol 

Some children with Down Syndrome have no serious health problems, but most have a mix of medical issues that need vigilance. Besides a paediatrician, children may need to see other specialists like a paediatric cardiologist because of the high instance of heart defects and need for surgery; ophthalmologist, otolaryngologist (ear, nose, and throat doctor), and audiologist.

With the average increase in the life expectancy of a person with Down Syndrome having increased to 60 years, it is important that parents, partners, employers, and the community in general understand their health needs. 

For the most part, their health needs are the same as a typically developing adult — screening, and prevention. The frequency of diagnostic tests is also the same as a typically developing adult. Additionally, persons with Down syndrome should be screened for sleep apnea, hypothyroidism, signs and symptoms of spinal cord compression and dementia. Patients with Down syndrome may have an unusual presentation of an ordinary illness or condition, and behavior changes or a loss of function may be the only indication of medical illnesses.
Caregivers must remember to obtain as detailed a history as possible given the limited verbal skills, and ensure that they are conditioned to communicate their medical needs since they have a decreased tendency to complain of pain.

Diagnosis 

The medical scientific community is yet to understand exactly why the condition happens. Some studies have found a link between the age of the mother and the occurrence of Down Syndrome in children — rise from 1 in 400 chance at age 35 to 1 in 100 by age 40 [5] — but these links remain hotly debated.

All said, there’s no way to prevent the chromosomal error that causes it. But the condition can be detected during pregnancy through screening tests followed up by diagnostic tests for confirmation.

Early detection of Down Syndrome can help parents prepare for a baby with additional needs by connecting with the community, educating themselves in advance, lining up support resources and services in order to be able start this journey on the front foot, thereby affording the child a better quality of life.

In India, one of the most commonly used scans is Combined First Trimester screening or NT scan [2]. It involves a highly specialised ultrasound assessment of the foetus for nuchal translucency (NT) at 12 weeks.

NT scan, blood test at 10 weeks and nasal bone data are combined with the mother’s age to arrive at a risk figure for birth defects and heart problems.

However, these scans are not conclusive and should be followed by diagnostic tests to look for changes in the chromosomes of the foetus.

  • Chorionic villus sampling (CVS) at 10-13 weeks
  • Amniocentesis at 15 weeks
  • Percutaneous umbilical blood sampling (PUBS) or second-trimester maternal serum test at 15 weeks
  • Detailed anatomy ultrasound at 20 weeks

Diagnostic tests such as CVS and amniocentesis can tell you whether or not a baby has a chromosome abnormality with more than 99% accuracy. However, these tests can never detect the severity of the condition.

Whatever the result, know that help is available. Talk to doctors, but also talk to parents. They will not only share resources, tips from their lived experience to prepare you, they will share the joy of having a child with Down Syndrome, the gifts such children really are.

References 

[1] https://www.cdc.gov/ncbddd/birthdefects/downsyndrome/data.html

[2] https://www.apollocradle.com/specialities/fetal-medicine/downsyndrome-screening/

[3] Shin M, Siffel C, Correa A. Survival of children with mosaic Down syndrome. Am J Med Genet A. 2010;152A:800-1

[4] https://www.ndss.org/about-down-syndrome/down-syndrome/

[5]https://www.parents.com/health/down-syndrome/are-you-at-risk-of-having-a-baby-with-down-syndrome/

[6] https://www.aafp.org/afp/2001/0915/p1031.html

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