Primary immunodeficiencies (PID) include >200 inherited disorders that affect the development and function of lymphocytes, neutrophils, eosinophils or monocytes. The first step in diagnosing a primary immunodeficiency is to suspect it. A good complete blood count (CBC) with differential count and peripheral smear is often the first investigation ordered when one suspects a PID. Trends in WBC counts and differentials are often more informative than a single abnormal value. Moreover, they should be always interpreted according to the age.
Neutrophilia is observed in phagocytic disorders such as leukocyte adhesion defects and chronic granulomatous diseases. Neutrophilic leukocytosis that persists in between episodes of infections has been characteristically described in leukocyte adhesion deficiency.
Neutropenia is a feature of several PIDs either as a result of decreased production of neutrophils or as a result of autoimmunity with increased destruction. (to be continued)……….