Jolan E Walter, MD, PhD, Robert A. Good Chair, Division Chief of Pediatric Allergy Immunology, University of South Florida at Johns Hopkins All Children’s Hospital, discusses when to consider primary immunodeficiency in cytopenias. Cases of patients with primary immunodeficiency and cytopenias include partial DiGeorge syndrome, autoimmune lymphoproliferative syndrome, primary immune regulatory disorders, such as CTLA4 deficiency, and bone marrow-based abnormalities, such as WHIM syndrome.