What is the most likely diagnosis for a 2-year-old boy with recurrent bacterial infections and increased absolute neutrophil counts?

In this case scenario involving a 2-year-old boy with recurrent bacterial infections and increased absolute neutrophil counts, the most likely diagnosis is leukocyte adhesion deficiency (LAD).

Leukocyte adhesion deficiency is a primary immunodeficiency characterized by the inability of leukocytes, particularly neutrophils, to migrate from the bloodstream to sites of infection. The defect is primarily due to a mutation in genes responsible for the production of integrins, which are adhesion molecules that facilitate the binding of leukocytes to the endothelium of blood vessels, allowing them to exit the circulation. Although these children have a normal or elevated number of neutrophils in the blood (which is why the absolute neutrophil counts are increased), they are unable to effectively reach and combat infections in tissues, leading to recurrent bacterial infections.

The other conditions listed have different mechanisms and clinical presentations. Chronic granulomatous disease involves a defect in the ability of neutrophils to generate reactive oxygen species, leading to issues in killing certain bacteria, but it typically does not result in elevated neutrophil counts. Myeloperoxidase deficiency also does not generally result in recurrent bacterial infections, as affected individuals can still produce other antibacterial substances. NADPH oxidase deficiency, which under