Nada Mukhtar Hassan Abdelkarim2017-07-252017-07-252015http://hdl.handle.net/123456789/4220Introduction Congenital hypothyroidism is the most common congenital endocrine disorder worldwide . Approximately 80 to 85% of cases are caused by defects in thyroid development (dysgenesis), the remaining 15 to 20% are due to errors of thyroid hormone biosynthesis (dyshormonogenesis) . Congenital hypothyroidism is also the most common preven table cause of mental retardation. Its neurological defects can only be reversible if diagnosed and treated early. I t s incidence rate is 1 out of 3000/4000 live births worldwide However, t his incidence rate is higher in developing countries such as Sudan ( 1 of 1400/2200 newborn infants ) in which its population is character ized by consanguinity (25 - 70%). The present study aimed to assess the demographic and clinical pattern of congenital hypothyroidism (dyshormonogenesis) in Sudan, to characterize TPO gene mutations in Sudanese patients with Congenital Hypothyroidism (dyshormonogenesis ) . Methods A total of 5 6 patients referred to Gaffar Ibn Auf Children Hospital presented with clinical features suggesting congenital hypothyroidism (dyshormonogenesis) were enrolled in this study. Demographic and clinical data was obtained by a predesigned questionnare. Five ml of venous blood were collected in EDTA tube from each patient under complete aseptic conditions for DNA extraction. All patients signed a written consent that has been approved by Al Neelain University Ethical Committee prior to the study. Genomic DNA was extracted using Guanidine Chloride method . Detection of TPO gene was performed by polymerase chain reaction (PCR) using primers for selected exons 7, 8, 9, and 14. Reaction products were electrophoresed on 1% agarose – TBE gels and visualized with XIII gel documentation system. Amplified region was directly sequenced to identify and characterize mutations in TPO gene. Data were analyzed using SPSS 13 software. Descriptive statistics (frequencies and percentages) were obtained for categorical variables. Genotype analysis was performed using Bio Edit program, Haploview program and Phyre bioscientific website for prediction of protein structure and configuration. Results Most patients enrolled in this study (85.7%) a re descendants of consanguineous marriage s. There were 11 reported families, comprising 74.3% of cases, with more than one affected member , o f th ose family members, 68.6 % were in fact siblings. Patients from consanguineous marriage had a 96.6% positive family history. The majority of patients (9 7.1%) developed complications. According to the tribal origin, the vast majority of patients (65.7%) were from Afro - Asiatic tribes, whereas 34.3% were from Nilo - Saharan tribes. There was a large variation in the geographical distribution of patients. Biochemical analysis and ultrasound findings were concordant with the genetic analysis results of patients. Sequencing analysis revealed apparent 18 single base changes (missense m utations) in exons 7, 8, and 9, and a deletion at exon14. Bioinformatics analysis showed strong L inkage D isequilibrium between two reported SNPs. Therefore they can be considered as potential genetic markers for disease association studies , population stud ies and neonatal screening. Conclusion Consanguinity, tribal marriages, and positive family history are factors that increase the risk of genetic disorders . Nineteen mutation including 8 novel mutations were detected. Strong LD between two SNPs is a potent ial g enetic marker for newborn screening of CH.(Molecular Biology