Symptoms:

• Abnormal nonverbal communication such as problems with eye contact, facial expressions, body postures, or gestures
• Being singled out by other children as "weird" or "strange"
• Failure to develop peer relationships
• Inability to return social or emotional feelings
• Inflexibility about specific routines or rituals
• Lack of showing, bringing, or pointing out objects of interest to other people
• Markedly impaired expression of pleasure in other people's happiness
• Preoccupation with parts of whole objects
• Repetitive behaviors, including repetitive self-injurious behavior
• Repetitive finger flapping, twisting, or whole body movements
• Unusually intense preoccupation with narrow areas of interest such as obsession with train schedules, phone books, or collections of objects

Signs and tests:

Physical, emotional, and mental evaluations are usually performed to rule out other causes.