en Genetics & Disease Genetics & Disease Original Article Original Article <p style="text-align: justify;">Cystic fibrosis (CF) is the most common severe autosomal recessive disorder caused by a wide spectrum of mutations in the gene encoding for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The frequencies, types and distributions of mutations vary widely between different populations and ethnic groups. The aim of this study was to perform a comprehensive analysis of the <em>CFTR</em> gene in an Iranian heterogeneous population. 20 CF patients diagnosed according to clinical evaluation and elevated sweat chloride value and presenting no common <em>CFTR</em> mutation, were analyzed for mutations and polymorphisms in exons 7, 20 and 21 and parts of introns 6, 7, 19, 20 and 21 of <em>CFTR</em> gene using PCR-sequencing. Sequencing of exon 7 revealed the presence of two variations c.864G>A (rs766189605) and c.910C>T (rs121909011) with the frequencies of 10% and 2.5%, respectively. c.864G>A is a synonymous variant that happens in amino acid valine 318 (GTG/GTA) and c.910C>T is a pathogenic missense variant that occurs at amino acid 334 (R334W) of CFTR protein leading to the change of arginine to tryptophan. Two variations c.3780A>G (rs1800130) and c.3783+117T>G (rs10155917) were also found in exon 20 and intron 20 with the frequencies of 7.5% and 5%, respectively. No mutation or polymorphism was found in exon 21. Ascertainment of <em>CFTR</em> mutation carrier frequencies and CF incidence among heterogeneous Iranian populations seems to be a necessity.</p> Cystic fibrosis, polymorphism, non-Caucasian, R334W 80 86 http://ibbj.org/browse.php?a_code=A-10-83-2&slc_lang=en&sid=1 Reza Tabaripoor tabaripoor@gmail.com 10031947532846001874 10031947532846001874 Yes Haleh Akhavan Niaki 10031947532846001875 10031947532846001875 No Mohammad Reza Esmaeili Dooki 10031947532846001876 10031947532846001876 No Tahereh Dadkhah 10031947532846001877 10031947532846001877 No Ali Mohammad Shirafkan 10031947532846001878 10031947532846001878 No Elham Ghadami 10031947532846001879 10031947532846001879 No Department of Genetics