A diagnostic flowchart of WHIM syndrome. WHIM syndrome should be suspected in patients with bacterial infections, refractory warts, or congenital heart defects, such as tetralogy of Fallot. The analysis of leukocyte counts in subjects with possible WHIM syndrome can reveal severe neutropenia (ANC reduced to below 500 cells per µL), monocytopenia, and lymphopenia, while immunoglobulin levels are not affected in all of the patients. Although myelokathexis can be observed in the majority of WHIM patients, CXCR4 genetic analysis should be performed in any patient with lymphopenia and neutropenia, despite whether the patient has a normal bone marrow morphology.