This patient meets criteria for autism spectrum disorder (ASD). ASD encompasses a group of heterogeneous conditions characterized by (1) persistent deficits in communication and social interaction associated with impairment in function and (2) repetitive behaviors that are inflexible and nonfunctional and interests that are often restricted. This patient's persistent problems with social communication and interaction, including difficulty with relationships and reading body language, adherence to routines, and repetitive behaviors, are consistent with this diagnosis. The DSM-5 has eliminated the subclassifications of autism (including Asperger syndrome) and merged all related entities into ASD.

Antisocial personality disorder is characterized by lack of remorse and disregard for others. Patients with this disorder usually have no regard for right and wrong. Although this patient has difficulty with social relationships, his symptoms are not consistent with antisocial personality disorder.

Although this patient's insistence on turning the light off and on three times and lining up his shoelaces nightly may be classified as obsessions, his difficulty with social relationships and communication make his clinical findings more consistent with autism than obsessive-compulsive disorder.

Social anxiety disorder is characterized by severe and persistent anxiety regarding social situations, including public speaking and meeting new people. Patients with this disorder may also have difficulty with social relationships accompanied by significant, often debilitating, anxiety. However, patients with social anxiety disorder do not have the restricted or repetitive behaviors that are associated with autism, as seen in this patient.