Estudios inmunológicos en ni？os con un episodio de infección bacteriana sistémica grave

infection is one of the most frequent causes of disease in children. pediatricians are frequently faced to ambulatory or hospitalised children with infection. sometimes, the severity or frequency of the episodes raises concern about the convenience of performing immunological studies. when these life threatening, bacterial systemic infections are repeated, immunological studies are mandatory. two or more such episodes are required by most authors to alert the physician to possible immunodeficiency. however, in immunodeficiencies, a second potentially severe and even fatal episode of infection may be the consequence of that policy. we show here three cases of primary immunodeficiencies presenting with systemic severe bacterial infections, and we discuss the immunological tests to be initially performed and the convenience of doing so after a first episode of systemic bacterial infection.