Autism spectrum disorder (ASD) is a developmental disorder that affects communication and behavior and typically manifests before 2 years of age. There’s wide variation in the type and severity of symptoms people experience. Individuals with Down syndrome, fragile X syndrome, and Rett syndrome are more likely than others to have ASD. ASD presents with symptoms that interfere with normal functioning, including:

• Difficulty with communication and interaction with other people, such as not making eye contact; failing to, or being slow to respond to someone calling their name or to other verbal attempts to gain attention; talking at length about a favorite subject without noticing that others aren’t interested.

• Restricted interests and repetitive behaviors, such as repeating words or phrases (echolalia); unusually high interest in topics like numbers and details; being more or less sensitive than other people to sensory input (for example, light, noise, clothing, or temperature).

DSM V includes autism, Asperger’s syndrome (a milder form of ASD), and pervasive developmental disorder under ASD.

Rett syndrome: Rett syndrome is a neurodevelopmental disorder that affects girls almost exclusively. It’s characterized by normal early growth and development followed by a slowing of development, loss of purposeful use of the hands, distinctive hand movements, slowed brain and head growth, hypotonia, problems with walking, seizures, and intellectual disability. Compulsive hand movements such as wringing, apraxia, walking on toes, teeth grinding, breath holding spells, seizures, etc. may be seen. Nearly all cases of Rett syndrome are caused by a mutation in the methyl CpG binding protein 2 or MECP2 gene. Mutations in the CDKL5 and FOXG1 genes are seen in individuals who have atypical or congenital Rett syndrome. Treatment is symptomatic, as there is no cure.

Oppositional defiant disorder (ODD): ODD is a pattern of angry/irritable mood, argumentative/defiant behavior, or vindictiveness lasting at least 6 months. It’s diagnosed when at least four symptoms from the categories below are present and occur during interaction with at least one individual who is not a sibling. Individuals with ODD do not show serious aggression toward others or serious antisocial behavior such as theft or property damage.

Angry/Irritable Mood including frequently loses temper, easily annoyed, often angry and resentful.

Argumentative/Defiant Behavior, such as often arguing with adults and authority figures, refusing to follow rules, deliberately annoying others, blaming others for his or her mistakes or misbehavior

Vindictiveness, at least twice during a period of 6 months.

For children younger than 5, the behavior should occur on most days for at least 6 months. For individuals 5 years and older, the behavior should occur at least once per week for at least 6 months.

Conduct disorder: Conduct disorder is a pattern of repetitive and persistent behavior that includes violation of basic rights of other people, rule-breaking, aggression, disregard for others, lying, drug use, or criminal activity that causes significant functional impairment. It’s diagnosed in children < 18 years of age. The same type of behavior in adults (< 18 years of age) is called antisocial personality disorder.