Immunodeficiency

Abstract Immunodeficiency is a condition caused by one or more immune system defects and is characterized clinically by increased susceptibility to infections with consequent severe, acute, recurrent or chronic disease. An immunodeficiency disorder should be considered in anyone with infections that are unusually frequent, severe and resistant; without a symptom‐free interval; from an unusual organism or with unexpected or severe complications. Immunodeficiencies may be either primary or secondary.