Every human has 23 pairs of chromosomes in each cell including one pair of sex chromosomes. These chromosomes are numbered from 1 to 22 (body chromosomes), and one pair of sex chromosomes is denoted as XX for females and XY for males.
Individuals with Down syndrome have an extra pair of chromosomes in the number 21 group. Thus, in the 21st group instead of one (2 nos), there is an extra chromosome (3 in place of 2). Hence, the condition is also known as Trisomy 21. British physician John Langdon Down was the first person who described the condition in 1866 and hence the name ‘Down syndrome’ was chosen for the condition. Approximately, about 1 in 700 live-born babies are suffering from this condition.
To signify the uniqueness of the triplication (trisomy) of the 21st chromosome which causes the particular condition, the 21st day of the third month (March) of the year is selected as World Down Syndrome Day.
Down syndrome can lead to some health complications, and they are at risk for congenital heart disease, respiratory disease, and an increased chance of leukaemia.
» Congenital heart defects
About 40% of children with Down syndrome are likely to develop chances of congenital heart defects. Treatment will be according to the type of cardiac abnormalities. In some cases, surgical interventions are required. In some other cases, follow-up is necessary. Atrio Ventricular Septal Defect is the most common congenital heart disease, then comes ventricular septal defect, atrial septal defect, and patent ductus arteriosus. If the baby is having cyanosis (blue baby), the defect is usually Tetralogy of Fallot (multiple heart defects).
These children may develop pulmonary hypertension if not treated appropriately. Even if there is no congenital heart disease, because of other abnormalities, pulmonary hypertension can occur.
» Respiratory issues
People with Down syndrome tend to have relatively narrow nasal passages and are hence prone to coughs and colds, especially in early childhood. Older people are also prone to chronic respiratory issues.
One of the common conditions is obstructive sleep apnea, which results in fatigue, stress, and behavioural issues in children. Snoring, brief cessation of breathing during sleep, rhinitis, and sinusitis are also common. Because of impaired immunity, people with Down syndrome are prone to upper respiratory tract infections and ear infections which are common in children less than 5 years. As told earlier, these children are to be followed up to evaluate the presence of pulmonary hypertension.
Children with down syndrome are more likely to develop leukaemia than other children. Acute myeloid leukaemia is the most common type of blood cancer seen in children less than 5 years. Hence, there is a recommendation to do a complete blood count at 6 months of age and then every year till 12 years of age.
The children may have hearing, vision, thyroid deficiency, and some other conditions like intellectual disability. The Indian Academy of Pediatrics, the academic body of paediatricians of India has published guidelines for parents in “Caring of a child with Down syndrome,” which is available for download through search engines like Google.
(Dr Babu George is Senior Consultant, Developmental Paediatrics, KIMSHEALTH)