Background Leukocyte adhesion deficiency type 1(LAD-1)is a rare, autosomal recessive inherited immunodeficiency dlsease characterized by recu rrent severe bacterial lnfection lmpal red pus formation poor wound healing associated with the mutation ln the CD18 gene responsible for the abilitv of the leucocytes to mig rate from the blood stream towards the site of lnflammation Correct and early dlagnosis of LAD-1 is vital to the success of treatment and prevention of agg ressive infections The pu rpose of this study was to collect the clinical findings of the disease and to identify the genetic entity. Methods CDl 8 expression ln the perlpheral blood leukocytes from the patient hls parents and normal control was measu red with flow cytometry The enti re coding regions of the CDl 8 gene were screened with direct sequencing genomic DNA Results CDl8 expression level on thls patient's leukocyte su rface was signlficantly decreased with normal level ln control g roup hls father and mother Gene analysis revealed that thls patient had a homozygous 899A>T missense mutation ln exon 8 of CDl 8 gene causlng the substitution of Asp to Val at the 300 amlno acid Hls parents were both heterOzvaOus carriers whlle no such mutation was found ln 50 normal controls Conclusion This study disclosed a novel point mutation Asp 300 Val located in a highly conserved region(HCR)of CD18 and confirmed the heteroqeneltv of the mutations causlnq LAD-1, lndlcating lt was qulte beneficial to establish correct and early dlagnosis ln chlIdren with severe LAD-1.