The goal of this study is to gain a better understanding of PTEN mutation syndromes to identify early markers and ultimately effective interventions for autism spectrum disorder. Individuals 18 months or older are eligible to participate if they have been diagnosed with PTEN hamartoma tumor syndrome. The study involves five visits over a two year period. Three of the visits occur on-site at a study location. The other two visits occur as phone calls. The on-site visits include a blood draw, physical/neurological exams and behavioral testing.