This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc., Subject name: Pathology
Delayed umbilical cord detachment leukocytosis is seen in? 
Select and explain. 
A. Leukocyte adhesion deficiency, B. Chronic granulomatous disease, C. Severe combined immunodeficiency, D. None of the above
A: Leukocyte adhesion deficiency
Answer: A: Leukocyte adhesion deficiency 
Explanation: Ans is 'a' i.e. Leukocyte adhesion deficiency * Delayed separation of the umbilical cord is pathognomonic for leukocyte adhesion deficiency (autosomal recessive). It's due to absence of CD 18 antigen that's necessary for formation of integrins, the substances that are responsible for the second step of leukocyte migration: adhesion. Because the leukocytes cannot efficiently reach the site of insult, they cannot engulf the offending substance, and no pus will be evident. Also, as a compensatory mechanism, there may be excessive leukocytosis.