Genetic predisposition

• ASD often runs in families
• Szatman

  combined data from various studies and calculated an overall sibling risk

  The risk was 2.2% compared to 0.11% for someone with no siblings with ASD

  20 times greater
• Bailey et al


  studied data from British twin study,focusing on twins where one had ASD

  In MZ twins,60% both had autism,concordance rate for DZ twins was 0%
• When looking at a broader definition,concordance rate was 92% for MZ twins and 10% for DZ twins
• Ronald et al


  looked at TEDS examining 3000 sets of twins

  Social characteristics are influenced by genetics,81-86% variation being attributed to genetic factors
• Bernier et al


  some families only have 1 member with ASD(simplex) others have multiple members with ASD or traits that have not be diagnosed(multiplex)
• In multiplex families ASD is likely inherited but in simplex families the cause is classed as 'de novo'.Meaning its a new mutation that happened during fertilisation.The mutation affects multiple genes
• Sebat et al


  10% of ASD cases are caused by de novo CNVS
• de novo CNVS occur when parents are older,age is a risk factor for simplex ASD
• Non-syndromic ASD is where its the main or only diagnosis without a clear cause
• Syndromic ASD is when it accompanies another primary condition with a know single gene gentic cause
• Example of syndromic is fragile X syndrome(FXS),a mutation in the FMR1 gene
• Zingerevich et al


  60% of the individuals also have ASD