Modes of genetic transmission of dyslexia in South Indian families

BACKGROUND: Dyslexia is a major educational problem, but the studies on genetics of dyslexia are very limited in India. There is a great dearth of proper statistical data to show the incidence of dyslexia in Indian population. More over inheritance pattern of dyslexia is not well established in our population. AIMS & OBJECTIVE: To establish the inheritance pattern of dyslexia in 23 selected families. MATERIALS AND METHODS: We have ascertained 23 dyslexic probands and their families from the state of Karnataka. Individuals with above 8 years of age, normal performance intelligence quotient (>85) and remarkable deviation in reading and writing skills compared to chronological age were considered for the study. Based on the genetic registry pedigrees of the families were constructed. RESULTS: Based on the affectedness, the dyslexia phenotypes were classified into four types: severe reading spelling deficit, mild reading spelling deficit, severe spelling deficit and mild spelling deficit. Severe dyslexia phenotypes were more frequent than mild phenotypes. Mild spelling deficits were better compensated than the other types. It was found that autosomal dominant inheritance pattern of dyslexia was more prevalent than autosomal recessive and sporadic pattern in the present study. CONCLUSION: Family history of dyslexia is a consistent risk factor; therefore this knowledge can be applied to the prevention and remediation of dyslexia.