Objective: Leukocyte adhesion deficiency (LAD) is one of the rare immunodeficiency diseases clinically characterized by recurrent severe bacterial infections, periodontitis, delayed umbilical cord separation, absence of pus formation, periodontitis, delayed wound healing, and often persistent leukocytosis. Three types of the disease were discussed. With autosomal recessive inheritance and a prevalence of 1 in 1,000,000 live births, Type I (LADI) is caused by mutations in the gene ITGB2, located on chromosome 21 (21q22.3), encoding for CD18 protein. More than 110 distinct mutations in ITGB2 gene have been identified and registered at Human Gene Mutation Database (HGMD; http://www.hgmd.cf.ac.uk/ac/all.php).This study aims to find the disease causing mutations in ITGB2 gene for helping future life in patient families via genetic counseling and prenatal diagnosis. Material and Methods: All of the patients with LAD1 diagnosis in the base of Flow cytometry (defect in CD18 and CD11 a, b, c) who were referred to IARRI during 2 years entered the study. 2 mL EDTA blood was obtained from all patients and their parents and genomic DNA was extracted. Polymerase chain reaction (PCR) for encoding exons and exon-intron boundaries of ITGB2 gene was performed. PCR results were direct sequenced in both orientations. Results: Sequencing amplified regions by PCR revealed a total of five different new mutations in five exons. These included three missense mutations, (c.382G>A in exon 6, c.715G>A in exon 7 and c.850G>A in exon 8) and two deletions (c.1907delA in exon 15 and c.1590_1594delCGGGC in exon 13). Mutation c.1907delA was found in two unrelated families. The last mutation was not previously reported. In fact, four out of 5 mutations have been reported previously. However, we find the mutation c.1590_1594delCGGGC neither in HGMD nor in other human mutation databases. Deletion of 5 nucleotides in this mutation results in a frame shift in open reading frame of CD18 protein and causes a premature stop codon at that position, p.Tyr530*. In all cases, mutation found in the patients was observed in their parents. Conclusion: The found mutations in this study can be used for genetic counseling and prenatal diagnosis of LAD I. [ABSTRACT FROM AUTHOR]