What is Down syndrome?
Down syndrome is also known as trisomy 21 syndrome. It is a genetic disorder that is characterised by recognisable physical features (mongolism), mental retardation and other associated medical problems. The way in which the syndrome expresses itself is highly variable between patients. About 15% of patients with severe Down syndrome die during the first year of life, whilst others show varying degree of signs and symptoms of the disease and can have a normal life expectancy.
Who gets Down syndrome and why?
It is estimated that Down syndrome occurs in approximately 1 in 700-800 live births. It is caused by a chromosomal disorder in which an error in cell division results in the presence of an additional third chromosome 21 or “trisomy 21”. Instead of the normal number of 46 chromosomes in each cell, the individual with Down syndrome has 47 chromosomes. This chromosome abnormality is called Standard Trisomy 21. It is the most common type of Down syndrome and occurs in 90-95% of cases. The two other variants of Down syndrome are called Translocation Trisomy 21 and Mosaic Down syndrome.
Apart from a few cases of Translocation Down syndrome, Down syndrome is not an inherited condition. A factor that does influence the incidence of Down syndrome is the age of the mother when she conceives. The incidence at various maternal ages is shown below.
|Maternal age (years)||Incidence of Down syndrome (live births)|
|15-29||1 in 1500|
|30-34||1 in 800|
|35-39||1 in 270|
|40-44||1 in 100|
|Older than 45||1 in 50|
What are the clinical features of Down syndrome?
The clinical features of Down syndrome include the characteristic physical, developmental and multisystem abnormalities. The physical features most recognised in patients with Down syndrome are:
- Flattening of the back of the head
- Slanting of the eyelids
- Small skin folds at the inner corner of the eyes
- Depressed nasal bridge
- Stumpy limbs and loose joint ligaments
Skin disorders in Down syndrome
Patients with Down syndrome are affected more often by chronic skin conditions and skin infections than the general population.
A newborn with Down syndrome will often have blue hands and feet at birth due to decreased blood circulation. This may be apparent for a few days and in some cases may develop into cutis marmorata, a skin condition characterised by bluish mottling all over the skin. Although this condition is common in many newborns, it may last several months longer in infants with Down syndrome.
Usually up until the age of 5 years the skin is soft and velvety. From 5 years and onwards skin changes start to take place and can become a major physical feature of Down syndrome. Chronic skin conditions and skin infections occurring commonly in patients with Down syndrome are described in the following tables.
|Chronic skin conditions||Features|
|Xerosis (dry skin)||
|Elastosis perforans serpiginosa||
|Bacterial infections||A variety of bacterial skin infections affect patients with Down syndrome regardless of whether they have associated atopic dermatitis.|
|Fungal infections||These frequently occur in adolescents with Down syndrome who are institutionalised.|
|Parasitic infections||People with Down syndrome are predisposed to crusted scabies infestation.|
What is the treatment for Down syndrome?
There is no specific treatment for Down syndrome. Treatment is directed at managing and preventing any complications that may arise.
Skin disorders are treated with various preparations, including emollients, topical medications and laser treatment. Click on individual skin disorders in the tables above for details on treatment options.