Hematologically important mutations: leukocyte adhesion deficiency (first update).

Leukocyte adhesion deficiency (LAD) is an immunodeficiency caused by defects in the adhesion of leukocytes (especially neutrophils) to the blood vessel wall. As a result, patients with LAD suffer from severe bacterial infections and impaired wound healing, accompanied by neutrophilia. In LAD-I, mutations are found in ITGB2, the gene that encodes the β subunit of the β(2) integrins. This syndrome is characterized directly after birth by delayed separation of the umbilical cord. In the rare LAD-II disease, the fucosylation of selectin ligands is disturbed, caused by mutations in SLC35C1, the gene that encodes a GDP-fucose transporter of the Golgi system. LAD-II patients lack the H and Lewis Le(a) and Le(b) blood group antigens. Finally, in LAD-III (also called LAD-I/variant) the conformational activation of the hematopoietically expressed β integrins is disturbed, leading to leukocyte and platelet dysfunction. This last syndrome is caused by mutations in FERMT3, encoding the kindlin-3 protein in all blood cells that is involved in the regulation of β integrin conformation.