Inclusion Criteria

• Individuals above the age of 18 months old at the time of consent who have documentation of a clinical diagnosis of autism spectrum disorder and/or a verified PTEN mutation from a medical or mental health professional for inclusion in the PTEN ASD, PTEN no-ASD or ASD macrocephaly groups.
• Macrocephaly (head circumference greater than or equal to 98th percentile) for inclusion in the ASD macrocephaly group.
• For youths, consent from parents or legal guardian. For adults, consent from self or legal guardian.
• Youths who are able (some young or severely impaired participants may not be able to provide assent) will be asked to provide assent as per IRB guidelines.
• Families with multiple children who meet the above inclusion criteria will be permitted to have as many children participate as they wish. A separate consent form will be filled out for each child enrolled in the study.
• Primary communicative language must be English

Exclusion Criteria

• Unwilling or unable to comply with study procedures and assessments
• Clinically significant medical disease that would prohibit participation in the study procedures.
• For subjects ELIGIBLE FOR OPTIONAL imaging biomarker assessment: contraindications to 3T MRI scanning, such as metal implants/non-compatible medical devices or medical conditions, including vagus nerve stimulator.
• For subjects ELIGIBLE FOR EEG/ERP biomarker assessment: contraindications to EEG/ERP, such as uncooperative or destructive behaviors preventing lead placement or capture by ERP/VEP equipment. Under age 2 or over 11 at the time of enrollment.