Recurrent infection in children: when and how to investigate for primary immunodeficiency?

While the impact of infectious diseases in developed countries has been diminished by improved nutrition, hygiene, vaccination coverage and health care, infections remain common, and even the healthiest children may suffer frequent infections, occasionally necessitating admission to hospital. When investigating a child with recurrent infections, it is therefore important to know the frequency, severity, infectious syndrome and infecting organisms which a normal child might experience, and to understand the impact of the child's underlying health on their susceptibility to infection. This paper examines infectious susceptibility in the healthy and immunocompromised child and explores the respective presentations of some primary immunodeficiencies.