In an adult patient with asymptomatic, isolated neutropenia in whom you suspect a Duffy null phenotype, at what ANC or in what situations would you do a bone marrow to look for other etiologies of neutropenia?  

What a great question! Happy to answer. As you know, as many as 60% of individuals who have the Duffy null phenotype will have an ANC that is lower than the lower limit of normal in many labs BUT as you also know, the total body (in circulation + in tissues) neutrophil count in such individuals is n...