Opportunistic infections (OIs) still remain a major cause of morbidity and death in children with either malignant or non malignant disease.
OIs are defined as those due to bacteria, fungi, viruses or parasites that normally do not cause disease, but become pathogenic when the body's defense system is impaired. OIs can also be represented by unusually severe infections caused by common pathogens. An OI could present itself at the onset of a primary immunodeficiency sindrome as a life –threatening event. More often OI is a therapy-associated complication in patients needing immunosuppressive treatment, among long-term hospitalized patients or in children undergo bone marrow or solid organ transplantation.
Aim of the present review is to provide a comprehensive and ‘easy to read’ text that briefly summarises the current available knowledge about OIs in order to define when an infection should be considered as opportunistic in pediatrics as a result of an underlying congenital or acquired immune-deficit.