Down syndrome is a genetic condition also called trisomy 21. In a trisomy, a person inherits an extra copy of one chromosome. Children with Down syndrome therefore have all or part of a third copy of chromosome 21, and the additional genetic material results in characteristic physical and intellectual features. It is the most common chromosome abnormality in humans and the commonest inherited cause of learning disability.
Down’s syndrome affects all ethnic groups equally, and affects more boys than girls. A child with Down’s Syndrome often looks different from other children, with a flat facial profile and eyes that slant upwards, smaller ears, a flat back of the head and protruding tongue with broad hands with a single crease across the palm.
Almost half of children affected have heart defects. Children with Down’s syndrome have moderate to severe learning disability. Like in autism, there is no cure for Down syndrome. Autism is a brain disorder, present from birth, but cause is unknown.
Children with autism have difficulty in learning language and social skills and in relating to people, and maybe aggressive or show self-injurious behaviour. Usually language is slow to develop, and may include peculiar speech patterns or the use of words without attachment to their normal meaning.
The autistic child often avoids eye contact, and may lack cooperative play with peers, due to an impaired ability to develop friendships, and underlying inability to understand other people’s feelings. Sometimes he may appear deaf or fail to respond to words or sounds; or be distressed by an everyday noise like a vacuum cleaner or a dog’s barking.