Abstract: We provide a set of novel mutations in HIST3H3, AMT, GLDC and PEX7 genes which we have discovered as causative of some autism spectrum disorders and/or intellectual disability after analysis of families with more than one affected child and with consanguineous parents. Based on some of these mutations, we also provide novel treatment options for autism spectrum disorders and/or intellectual disability wherein the novel mutations have been diagnosed. The invention is based on the discovery that certain specific mutations, particularly when present in a homozygous, compound heterozygous, or trans heterozygous combinations, result in a phenotype of an autism spectrum disorder and/or intellectual disability. Some mutations also cause the disorder or disease as heterozygous mutation.