Introduction- Multiple evidence indicate a strong genetic contribution to PDDs manifesting as increased risk in siblings. However there is no Indian data available on this, hence this study was done.

Method-Study was done at tertiary care hospital in India. Patients of PDD who had siblings in the age group 2-14 yrs were approached. Siblings in age group 2-4 years were screened using Modified Checklist for Autism in Toddlers (M-CHAT), and those in age group 4-14 years were screened using Social Responsiveness Scale (SRS), parent version.For Hindi-speaking population, pre-tested Hindi translations of both the questionnaires were used. Screen positive siblings were assessed using DSM-IV criteria by a Developmental Pediatrician. Risk of PDD in siblings was correlated with various familial and disease characteristics of the index case.

Results-204 siblings (104 females/100 males) were screened (34-MCHAT and 170-SRS). 13 were screen positive. 3 were lost to follow up. Rest 10 who were assessed on DSM-IV criteria were classified as PDD-NOS (3) and Autism (7).Prevalence of PDD in siblings was 4.97%. There was a significant effect of the presence of aggressive behaviour, externalizing and total problems in proband [as assessed by Childhood behaviour checklist (CBCL)], and the young age of father at conception on the sibling risk of PDD.

Discussion/Conclusion- The previously described increased risk of PDD in siblings of patients with PDD is also seen in our population. Thus genetic counselling of family for increased risk and routine screening of siblings should be done with the diagnosis of children with PDD.