<prompt> Autism is characterised by-Biological causationPervasive social and language communication problemMetabolic diseaseMainly due to hypothalamic damage  <response>: Autism spectrum disorder ASD was previously known as Pervasive Developmental disorders, a phenotypically heterogenous group of neurodevelopmental syndromes, with a polygenic heritability. ASD was conceptualised as five discrete disorders, including autistic disorder, Aspergers syndrome, Childhood Disintegrative Disorder, retts syndrome and Pervasive developmental disorder not otherwise specified. Current understanding on Etiology of Autism includes- Genetics, Biomarkers abnormal signaling in 5HT system, mTOR linked synaptice plasticity mechanisma, alterations of GABA inhibitory system, Immunological factors, Prenatal Perinatal factors, Comorbid neurological disorders and Psychosocial theories. Ref: Synopsis of Psychiatry, 11e, pg 1152 to 1155. 