Autism is a disorder of neural development characterized by impaired social interaction, and communication, and by restricted and repetitive behaviour. Autism affects information processing in the brain by altering how nerve cells and their synapses connect and organize. It’s one of the three recognized disorders in the autism spectrum (ASDs) the other two being Asperger syndrome, pervasive development disorder, not otherwise specified, commonly abbreviated as PDD-NOS
Signs and Symptoms
Signs of autism may appear during infancy and the disorder is usually diagnosed by the age of three. Sometimes the child’s development appears normal until about two years old and then regresses rapidly .Symptoms of Autism occur in various combinations from mild to severe. Infants with the disorder often display abnormal reaction to sensory stimuli (i.e. senses may be over-or underactive).Touches may be experienced as painful, smell may be overwhelmingly unpleasant, and ordinary daily noises may be painful. Loud noises (e.g. motorcycles going by, vacuum cleaner) and bright light may cause inconsolable crying.
Other signs of the disorder in infants include the following:
Appears indifferent to surrounding
Appears content to be alone, happier to play alone.
Displays lack of interest in toys.
Displays lack of response to others.
Does not point out objects of interest to others (called protodeclarative  pointing)
Marked reduction or increase in activity level
Resists cuddling.
Young children with autism usually have impaired language development. They have difficulty expressing needs (i.e use gestures instead of words) and may laugh, cry or show distress for unknown reasons. Some children develop rudimentary language skills that do not serve as an effective form of communication.

Autistic children do not express interest in other people .They may resist changes in their routine, repeat actions (e.g. turn in circles, flap their arms) over and over .
Symptoms in young children include the following:
Avoid cuddling or touching.
Frequent behavioral  outburst, tantrums.
Inappropriate attachments to objects .
Maintains little or no eye contact
Over or under sensitivity to pain, no fear of danger.
Sustained abnormal play.
Uneven motor skills.
Unresponsiveness to normal teaching methods and verbal clues(may appear to be deaf despite of normal hearing)
Lack of creativity, Pretend play   Echolalic-copies words like a parrot
Variety is not the spice of life   Joins in only if an adult insists and assidts
Talks incessantly about one topic   Bizarre behaviour
Displays indifference   But some can do some things very well,very quickly, but not tasks involving social understanding