Objective: Hereditary hearing loss (HHL) is a very common disorder. When inherited in an autosomal recessive manner, it typically presents as an isolated finding. Interestingly and unexpectedly, in spite of extreme heterogeneity, mutations in one gene, GJB2, are the most common cause of congenital severe-to-profound deafness in many different populations. In this study, we assessed the contributions made by GJB2 mutations and deletion in a portion of GJB6 to the autosomal recessive non-syndromic deafness genetic load in Iran.

Materials & Methods: In this descriptive and cross – sectional study1605 probands from 1605 different nuclear families with autosomal recessive non-syndromic hearing loss were investigated. Hearing loss tests and clinical examination were done and 10 ml blood was drawn as DNA source. After study of 35delG mutation by ARMs PCR, negative or heterozygote individuals were sent to IOWA University for detection of other GJB2 mutations. 

Results: GJB2-related deafness was found in 243 families (15.1%).

Conclusion: Varient geographic pattern for GJB2-related deafness has considerable results in Iran in comparable with other study in Europe and our neighboring countries and deletion in GJB6. [∆ (GJB6-D13S1830)] hasn't been detected in our studied population.

Objective: About 70 percent of mental retardation can be attributed to genetic causes. Whereas the recognization of genetic causes of mental retardation causes better programming and more precision council for prevention and control of mental retardation, so the aim of this study is to investigate the genetic causes of mental retardation in Golestan province.

Materials & Methods: In this descriptive research which is a cross-sectional and applied study, fifty families with two or more affected children from different parts of Golestan province were collected with cooperation of Golestan state welfare organization and by simple sampling method. Mental retardation of affected people had been previously proved by physicians. Blood samples of patients and controls in the family were prepared. Patients were investigated for dysmorphism and microcephaly. Cytogenetic study, metabolic test, fragile X test, and linkage analysis for seven gene loci known for autosomal recessive primary microcephaly (MCPH) was carried out.

Results: Chromosomal abnormalities were not observed in any family. One out of fifty families revealed fragile X syndrome and ten were affected to MCPH. Five out of ten microcephaly families were linked to MCPH (autosomal recessive primary microcephaly) loci.

Conclusion: Autosomal recessive primary microcephaly (MCPH)make up about 20% 0f all mental retardation in Golestan province. This prevalence is very remarkable.

Objective: The aim of this study was to investigate the genetic causes of autosomal recessive intellectual disabilities (AR-ID) in Hamadan province of Iran.

Materials & Methods: In this descriptive-analytical cross-sectional study, 25 families with more than one affected with putative autosomal recessive intellectual disability were chosen with collaboration of Welfare Organization of Hamadan province. Families were included a total of 60 patients (39 male and 21 female) whose intellectual disability had been confirmed by Raven IQ test. Each family was asked for clinical examination and getting consent form. Blood sample was collected from each family. One proband from each family was tested for CGG repeat expansion in FMR1 gene, chromosomal abnormalities and inborn errors of metabolism. We also performed homozygosity mapping based on STR markers for seven known MCPH loci in families with primary microcephaly and AR-ID.

Results: Five families had full mutation of Fragile X syndrome. No chromosomal abnormalities were identified. Metabolic screening revealed one family with Medium Chain Acyl CoA Dehydrogenase deficiency. None of three families with primary microcephaly and AR-ID showed linkage to any of known seven MCPH loci.

Conclusion: The main causes of ID in Hamadan province were Fragile X syndrome and Autosomal Recessive Primary Microcephaly with the frequencies of 20% and 12%, respectively.