A 4-year-old boy presents with persistent leukocytosis. Patient history reveals that the boy has suffered from recurrent infections. On physical examination, the physician notes severe growth and mental retardation. An additional feature of this child is that he harbors the rare Bombay (hh) blood type at the ABO locus. These findings are consistent with the child suffering from which of the following disorders?

Question

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Leukocyte adhesion deficiency syndrome II (LAD II) is characterized by persistent leukocytosis, recurrent infections, growth and mental retardation, and the rare Bombay blood type due to a defect in fucose metabolism affecting blood group antigen expression.  The child is suffering from LAD II, which is a disease that belongs to the class of disorders referred to as primary immunodeficiency syndromes. Symptoms of LAD II are characterized by unique facial features, recurrent infections, persistent leukocytosis, defective neutrophil chemotaxis, and severe growth and mental retardation. The genetic defect resulting in LAD II is in the pathway of fucose utilization leading to loss of fucosylated glycans on the cell surface. An additional feature of LAD II is that individuals harbor the rare Bombay (hh) blood type at the ABO locus as well as lack the Lewis blood group antigens. The recurrent infections seen in LAD II patients are the result of the defective neutrophil function. Neutrophils are involved in innate immunity responses to bacterial infection. To carry out their role in host defense mechanisms, neutrophils must adhere to the surface of the endothelium at the site of inflammation, which is an event mediated by cell surface adhesion molecules. The selectin family (E-, L-, and P-selectins) of animal lectins are necessary to mediate the initial process of neutrophil adherence to the endothelium. The selectins recognize sialylated fucosylated lactosamines typified by the Lewis X antigen.

A 4-Year-Old Boy Presents with Persistent Leukocytosis