USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

In patients with Leukocyte Adhesion Deficiency (LAD), the underlying defect is in the ability of leukocytes to adhere and migrate to sites of infection due to a lack of integrins necessary for cell-cell adhesion. This leads to a unique array of clinical presentations.

Delayed separation of the umbilical cord typically occurs in LAD due to the failure of leukocytes to migrate and respond to infection at the umbilical cord site, causing the cord to remain attached longer than usual.

Severe gingivitis is another hallmark of LAD. The inability of neutrophils to reach the gum tissues results in inflammation and infection, manifesting as gingivitis, which can be recurrent and severe.

Peripheral blood neutrophilic leukocytosis is commonly seen in LAD because, despite the high levels of circulating neutrophils, these cells cannot effectively exit the bloodstream and enter the tissues where they are needed, leading to accumulation in the blood.

Recurrent skin abscesses with pus formation, however, is not a typical symptom of LAD. While patients may experience skin infections, these abscesses do not usually form pus due to the impaired ability of neutrophils to respond appropriately to localized infections. Instead, infections may be more superficial and present without the typical pur