How does Down syndrome affect the body?

Recognising the signs and symptoms

• Infants: A baby will likely reach normal milestones such as rolling over, sitting, standing, talking and walking, but at a much slower pace that would be expected.
• Children: Developmental disabilities can lead to problems with overall behaviour. If severe, serious problems with communication and understanding the expectations of others can result in oppositional defiant disorder (defiant or disobedient behaviour towards authority figures, often displaying persistent patterns of irritability, anger, vindictiveness or arguing).
• Adolescence: Puberty (onset of teenage years) typically begins around the same time as for others (slightly delayed for males), but can be a particularly challenging time for an individual with Down syndrome. Social difficulties and vulnerabilities result in strong emotions and feelings. The danger is allowing these highly sensitive factors to develop into mental health problems, such as depression.
• Adulthood: Female individuals can usually reproduce, but are likely to experience early menopause (around the age of 40). It is common for males with Down syndrome to be unable to father children (as they are often sterile).

The general physical characteristics of Down syndrome include:

• A flattened nose (nasal bridge) or general facial features
• Back of the head that is flattened
• Small ears (sometimes oddly shaped or set low on the head)
• Small head and overall stature
• Short limbs
• Small mouth
• Protruding (bulging) tongue (often sticks out of the mouth)
• A narrow palate (the roof of the mouth may also form a little high with a downward curve)
• Crooked teeth (delayed development of teeth which also do not form in the same order as others)
• Upward slanting eyes
• Palpebral (oblique) fissures of the eyes (upward slanting of fissures in the elliptic space between the eye lids)
• Epicanthal fold (the inner corner of the eye has a rounded fold of skin)
• Brushfield spots (white spots on the coloured portion of the eyes – the iris)
• Short neck (with excess skin and fat)
• Short, broad hands and short fingers
• A single palmar crease (a single crease that extends across the palm / centre of the hand)
• An individual flexion furrow (a crease made by folding, pressing or wrinkling, usually on the fifth finger)
• A large space between the large and second toe on the feet
• Loose joints
• Excessive flexibility

Babies with Down syndrome may also show signs of decreased muscle tone (hypotonia or floppiness) shortly after birth. As a child grows abdominal muscles (belly muscles) which are low in muscle tone can protrude (stick out). A baby may be born at a normal size, but does not typically grow and develop at an expected healthy pace. Babies experience delayed growth, often not reaching the average expected height or achieving developmental milestones at the rate normal infants and children would.

Cognitive impairment

Normal cognitive development is also a distinctive characteristic of Down syndrome. A person with the condition will experience difficulties in learning (cognitive function), thinking, reasoning and understanding for their entire lifetime. Intellectual disability is quite variable but is usually mild or moderate and can be appropriately managed.

Scientists do not yet have a clear understanding as to which of the several hundred genes in chromosome 21 directly impact cognitive ability. The cause of this dysfunction is thus largely unknown, but it has been determined that the average brain volume is smaller than that of an unaffected person. The hippocampus and cerebellum (brain structures) do not function effectively. Normally, memory function (short and long-term) and learning ability is made possible in the hippocampus structure of the brain.

Speech delays and slow development of fine motor skills are also key characteristics. Skills such as sitting, standing and walking take longer to develop. It may be a little difficult to understand the speech of a person with Down syndrome as well. Speech therapy can help with expressive language and overall communication.

Children are capable of being taught how to learn and lead fairly individual lives but need appropriate help whilst growing up, often requiring additional assistance through the schooling years.

Individuals with Down syndrome typically learn continuously, slowly picking up new skills throughout their lives. This applies physically and mentally, as well as when it comes to developing social skills. A gradual decline in thinking ability may occur as an individual reaches the age of 50. This places a person at risk of disorders whereby a gradual loss of memory and judgment occur at a far earlier age than a normally developed person.

Delays in both mental and social development can also result in:

• Poor judgement skills
• A short attention span
• Difficulties with social interaction (as a result of communication problems)
• Impulsive, or obsessive / compulsive behaviour
• Behavioural issues such as stubbornness and tantrums

Associated medical conditions

• Congenital heart defects: Almost half of all babies born with Down syndrome have a heart defect. The most common of which is an atrioventricular septal defect (the formation of holes between the left and right chambers of the heart and malformation of the valves that control blood flow between the heart’s chambers). Other congenital heart defects common among new-borns with Down syndrome include atrial septal defect (a hole in the wall of the upper heart chambers), ventricular septal defect (an abnormal connection between the heart’s lower chambers), patent ductus arteriosus (the opening between two blood vessels leading from the heart fails to close following birth) and tetralogy of Fallot (a combination of 4 heart defects that result in oxygen-poor blood flow from the heart to the rest of the body). Surgery may be required for new-borns shortly after birth.
• Gastrointestinal or digestive abnormalities: The most common impairments and abnormalities that occur (some of which are congenital) include tracheoesophageal fistula (an abnormal connection or fistula between the oesophagus and the trachea), oesophageal atresia (the lower ends of the oesophagus do not connect with the stomach), Hirschsprung's disease (disease of the colon causing severe constipation and difficulty passing stool), duodenal atresia (abnormal development of the small bowel or duodenum) or stenosis (narrowing of the duodenum) and an imperforate anus (the opening of the anus is either blocked or missing since birth). Later in life, some individuals can also develop coeliac disease. Congenital defects may require surgery during infancy to be corrected.
• Cancer and tumours: Cancers of blood-forming cells can occur, such as leukaemia - Myeloid leukaemia and lymphoblastic leukaemia, as well as testicular cancer.

Other medical conditions which can occur include:

• Otitis media and other ear infections
• Hearing loss
• Infantile spasms
• Seizures
• Delayed tooth growth (resulting in chewing difficulties)
• Visual abnormalities, changes and impairments such as poor vision and cataracts
• Sleep apnoea
• Hypothyroidism (underactive thyroid)
• Dental problems
• Constipation problems (chronic)
• Gastroesophageal reflux
• Cervical spine instability
• Hip dislocations
• Obesity (or being overweight)
• Frequent susceptibility to infections (respiratory infections, urinary tract infections and infections of the skin)
• Dementia
• Early-onset Alzheimer’s disease
• Behavioural and co-existing psychiatric disorders such as ADHD (attention deficit hyperactivity disorder), autism spectrum disorders, OCD (obsessive compulsive disorder), stereotypical movement disorders and depression.

Many children with Down syndrome may not begin their lives with congenital defects and lead relatively healthy lives (with occasional infections or other mild, but treatable problems). For others, overall health problems are more severe or more frequent. Usually those born with congenital defects have the most frequent health problems as they grow.