What is Down's syndrome?
Down's syndrome (also referred to as trisomy 21) is a genetic disorder characterised by an extra copy of the chromosome 21. Chromosomes are molecules which organise our DNA into compact units in the nucleus of the cell. A healthy cell has two copies of every chromosome, whereas people with Down syndrome have an extra copy of a single chromosome.
Down's syndrome leads to physical and metal developmental delays and disabilities. It is the most common genetic disease in the world, present in between 1 in 400 to 1 in 1500 newborns [1, 2, 3].
Genetic Basis of Down's Syndrome
The principal basis of Down's syndrome is the presence of additional genetic material in the extra copy of the chromosome 21. This in turn changes the gene dosage of some of the genes of chromosome 21 (the chromosome contains 500 - 800 genes), which in turn causes the developmental alterations. Gene dosage is a measure of a copy number of genes which can lead to more or less pronounced effect of those genes [2, 4, 5].
While Down syndrome is generally known as trisomy 21, there are three types in which Down syndrome can manifest:
- Trisomy 21 - the most common type of Down syndrome, where every cell has an extra copy of chromosome 21.
- Mosaic trisomy 21 - this occurs when an extra copy of chromosome 21 is present in some cells, but not in every cell.
- Robertsonian translocation - there is an extra part of chromosome 21, however it is not a complete copy [1, 6, 7].
Symptoms of Down Syndrome
Individuals with Down syndrome exhibit certain characteristic signs. These can be more or less pronounced, and include:
- flat facial features,
- small head and ears,
- short neck,
- bulging tongue,
- eyes slanting forward,
- atypically shaped ears,
- poor muscle tone.
This is usually also accompanied by a degree of developmental disability, which can manifest as impulsive behaviour, poor jugement, short attention span and learning difficulties.
Infants with Down syndrome are usually born at average size, but develop more slowly [1].
Complications Associated with Down Syndrome
Down syndrome is associated with a range of possible medical complications. These may include:
- congenital (present at birth) heart defects,
- hearing loss,
- problems with vision and/or cataracts,
- hip and joint issues,
- increased incidence of leukaemia,
- chronic constipation and other digestive issues,
- sleep apnea,
- dementia and Alzheimer's disease later in life,
- hypothyroidism,
- obesity,
- increased incidence of infections (respiratory, skin, urinary tract) [1].
Down syndrome in the black population
The prevalence of Down syndrome in the black population varies between regions and different studies, however, broadly speaking, black people do get Down syndrome.
In a study conducted in Cape town, South Africa, the prevalence of Down's syndrome was found to be 1.29 per 1000 in the local black population [8]. In Atlanta, US, a population-wide study concluded no correlation between race / ethnicity and the prevalence of down syndrome, suggesting that Down syndrome is equally prevalent across racial groups [9].
In KwaZulu-Natal, South Africa, the prevalence of Down's syndrome was noted to be 0.8 per 1000. However, the study concluded that diagnosing Down syndrome is a public health challenge in the region, likely leading to missed diagnoses [10].
In the United States, a population-wide study found that the prevalence of Down's syndrome in the black individuals was lower than in the white individuals [11]. However, another study concluded that the rates are equal across races at birth. This, however, can change later in life as black / African American infants with Down syndrome have a lower chance of survival beyond the first year of life [12].
Healthcare Outcomes in Black Population with Down Syndrome
Sadly, research has shown that healthcare experiences and outcomes for patients of black, African American or African descent or mixed race differ from the white patients, sometimes regardless of Down syndrome. Physicians, caregivers and patients alike expressed concerns that patients of colour with Down syndrome receive a lower quality of medical care [13].
When asked in a study, caregivers reported feeling tired of being reminded of the patient's race by the medical community, and experienced willingness to learn more about caring for people with Down syndrome [13].
Medically, prenatal drug use and intubation were found to be more frequent in black children with Down syndrome compared to the rest of the population. There were also significant increases in referrals to cardiology for black children with Down syndrome younger than 5 years; this points to an increased incidence of congenital heart disease in these populations [14].
Improving Healthcare Outcomes
Following the data on outcomes, there is a need for more race concordant medical providers and increased awareness of Down syndrome in the black population [13].
Additionally, access to supportive care for people with Down syndrome should be made easier (logistically and financially) - these could include:
- physical therapy,
- occupational therapy and speech therapy,
- developmental specialists,
- dietitians,
- educational advocated [15].
Additionally, there is a need for better advertisement of clinics specialising in Down syndrome care, particularly in low-income communities. There are barriers to access, such as travel time and cost, preventing patients from seeking optimal care, and removing them could potentially improve the health outcomes in the black populations with Down syndrome [15].