Autism spectrum disorder is a spectrum of neurodevelopmental disabilities that predominantly affect social, communication, and behavioral skills, often with restricted and repetitive patterns of behavior. Symptoms typically present before age 2 years. Phenotype severity can vary considerably, with some patients having minimal to no verbal skills while other autistic individuals can function highly in the general population. Some patients have delayed milestones from birth, others plateau, and some demonstrate regression of communication and language skills. This spectrum includes conditions that were previously diagnosed individually, such as autistic disorder, pervasive development disorder, childhood disintegrative disorder, and Asperger disorder.

Clinical features include lack of social reciprocity, unawareness of others, and lack of interest and empathy for others. Patients may lack joint attention (social referencing), be unable to interpret nonverbal communication, or have difficulty with social relationships. They may exhibit restricting and repetitive behaviors, such as hand flapping, rocking, or walking on tiptoe. Affected individuals may be inflexible in specific daily routines or rituals. Many patients have aberrant sensory processing abilities highlighted by heightened sensitivity to texture, sounds, or touch. Other observed features include motor deficits, macrocephaly, speech difficulties (including nonverbal), and savant abilities.

Males are 4 times more likely to be affected. The incidence of autism spectrum disorders has increased in recent years, although the underlying etiology is not well understood. There appear to be genetic factors and potentially environmental factors, although neither are clearly defined.

Affected patients will require specialist involvement and an individualized management plan.