Evaluation of 24 Bp Duplication of Chitotriosidase Gene in Pulmonary Tuberculosis in Zahedan, Southeast Iran: A Preliminary Report

Background: Chitotriosidase (CHIT1), the major chitinase in human airways, is expressed by pulmonary macrophage. Variation in the coding region with 24 bp duplication allele results in reduced CHIT1 activity. Objectives: The present study was designed to assess the impact of 24 bp duplication in exon 10 of human CHIT1 gene on pulmonary tuberculosis (PTB) risk. Patients and Methods: This case-control study was performed on 173 PTB patients and 164 healthy subjects in Zahedan, southeast Iran. Polymerase chain reaction (PCR) was used to detect the variant. Results: Homozygous wild type, heterozygous and homozygous mutant frequencies of CHIT1 24 bp duplication polymorphism were 43.9%, 43.9% and 12.2% in controls and 42.8%, 45.1% and 12.1% in PTB patients. We found the mutant allele frequency of 34.2% and 34.7% in controls and cases, respectively. Chi-square comparison of PTB and control subjects and logistic regression analysis revealed no association between CHIT1 24 bp duplication and PTB. Conclusions: In conclusion, CHIT1 24 bp duplication might not be a candidate gene for susceptibility to PTB. Larger studies are necessary to confirm these findings in various populations.