Leucocyte adhesion deficiency (LAD) is a group of rare autosomal recessive (<1:1 000 000 births) inherited disorders characterised by immune deficiency and peripheral neutrophilia. Three types of LAD syndrome have been distinguished. LAD type 1 (LAD-I) is the most common. It results from a mutation in the integrin â 2 (ITGB2) gene that codes the ITGB subunit (CD18 antigen). Since 1970, it has been reported in more than 300 children worldwide. It is characterised by delayed separation of the umbilical cord, recurrent bacterial and fungal infections, defective wound healing, blood neutrophilia and a high mortality rate at an early age. We report the second fatal case of an infant with LAD-I diagnosed in Chile, with developmental delay associated with a congenital cytomegalovirus infection. CD18/CD11 expression was normal. Genetic analysis of CD18 revealed a homozygous mutation in ITGB2, viz. c.1835G>T; p.C612F, and led us to suspect a biological parent other than the legal father and, therefore, an unwanted social situation.