 Several disease-linked point mutations have been identified, and those who are heterozygous for a point mutation are healthy, but those who are homozygous develop clinical disease.The number of disease-causing genotypes keeps increasing as more mutations are discovered, and now thirty different point mutations have been identified so far, and one deletion, that cause adenylosuccinate lyase deficiency.When the substrates of ASL (adenylosucinate and SAICAR) build up due to enzyme deficiency, they are dephosphorylated and turn into succinyladenosine (S-Ado) and succinylaminoimidazole carboximide riboside (SAICA riboside).