A rare immunodeficiency with an autosomal recessive pattern of inheritance. It is caused by mutation in the ITGB2 gene on chromosome 21 which codes for the beta subunit of beta-2 integrin (CD18). The mutation results in significantly reduced or absent expression of CD18 on the surface of leukocytes which impairs their ability to migrate and interact with antigens. Initial clinical signs include omphalitis and delayed separation of the umbilical cord. The clinical course is marked by recurrent bacterial and fungal infection without pus formation. In instances where there is < 1% expression of CD18, prognosis is dismal with a high likelihood for life-threatening infection within the first year of life. [ ]