OVERVIEW
Leukocyte adhesion deficiency (LAD) type II (LAD II) is a rare primary immunodeficiency disease with only 2 cases reported to date.LAD II is an abnormality in fucose metabolism, resulting in defects in the leukocyte surface-selectin ligand fucosylation antigen SLEX, which leads to abnormal rolling function of leukocytes and affects their adhesion to the vascular endothelium.
Etiology
The SLEX antigen on the surface of leukocytes serves as a ligand-binding site for selectins on the surface of endothelial cells, which is involved in the mutual adhesion of leukocytes and endothelial cells and promotes leukocyte rolling toward the inflammatory region. Abnormal fucose metabolism, which results in the absence of fucosylated substances such as the SLEX antigen of selectin ligands, leads to leukocyte adhesion dysfunction, growth and retarded intellectual development.
Symptoms.
Recurrent bacterial infections occur shortly after birth and include pneumonia, periodontitis, otitis media, limited soft tissue infections, and skin infections. The absence of pus formation at the site of infection is characteristic. The infections are less severe than LAD I and there is no delayed cord detachment. Other manifestations are severe mental retardation and short stature with peculiar facial features.
Examination
Peripheral blood neutrophils are abnormally high, even in the absence of infection, up to (25-30) × 109/L, and in acute infection up to 150 × 109/L. Neutrophil chemotaxis is markedly decreased and phagocytosis is normal. The use of monoclonal antibodies revealed no SLEX expression in the neutrophils of the child. The half-life of neutrophils in the vasculature was only 3.2 hours (6-9 hours in normal subjects), and the metabolic rate was also significantly elevated, with eight times as many neutrophils being released from the bone marrow into the bloodstream as in normal subjects.
All auxiliary examinations are usually selected according to clinical needs, and chest radiographs and ultrasound are often required.
Diagnosis
The diagnosis is confirmed by recurrent infections without pus formation, by the presence of peculiar facial features and mental retardation, and by a history of parental consanguineous marriages combined with laboratory tests.
Treatment
Antimicrobial therapy is effective in controlling bacterial infections and prophylactic use of antimicrobials is usually not required. Chronic periodontitis and severe mental retardation are difficult to resolve. Dietary supplementation with fucoidan or administration of an intravenous supply of fucoidan may be considered. Children are often erythrocyte H antigen negative (H antigen also belongs to fucosylated antigen), if repeated administration of intravenous fucose is given, the body can be induced to produce anti-H antigen antibodies, resulting in severe hemolytic anemia, and should be used with caution.
Prognosis
Repeated infections to nutritional deficiencies and growth retardation, severe infections may lead to death of the child, and severe mental retardation is difficult to resolve.