Primary antibody deficiencies (PAD) constitute the majority of all primary immunodeficiency diseases (PID) also termed inborn errors of immunity (IEI). This category (PAD) represents around 52% of all IEI and the proportion overall is still greater given that antibody deficiency is a component of other groups including combined and severe combined immunodeficiencies (SCID), autoinflammatory disorders, diseases of immune dysregulation and other well-defined PIDs.
Secondary antibody deficiencies (SAD) represent a larger and expanding number of individuals resulting from the use of a wide range of immunosuppressive therapies, in particular those targeting B cells, and may also result from renal or gastrointestinal immunoglobulin losses, infections, for example, HIV or malaria, malnutrition or others.