People who are immunocompromised are affected more frequently and severely by infections.
The term immunocompromised (or immunosuppressed) refers to people who have an ‘immunodeficiency’ or a weakened immune system, meaning their ability to fight infections and diseases is reduced (NIS n.d.)
There are two types of immunodeficiency:
Primary immunodeficiencies: chronic, genetic disorders causing an individual to be born without some immune defences or with an impaired immune system; and
Secondary immunodeficiencies: immunodeficiencies acquired from environmental factors such a disease.
(Mayo Clinic 2020; British Society for Immunology 2017)
Primary immunodeficiencies comprise over 400 disorders that are caused by defects in the immune system. Consequently, the immune system functions less efficiently than normal, potentially causing complications. These disorders are often inherited (ASCIA 2019).
Primary immunodeficiencies may be mild and evade detection for years, or they may be severe enough to be noticed right at birth (Mayo Clinic 2020).
They fall broadly into one of six categories depending on which part of the immune system has been impacted:
Humoral immunity (B cell) deficiencies, which account for about 50 to 60% of primary immunodeficiencies;
Cellular immunity (T cell) deficiencies, which account for about 5 to 10% of primary immunodeficiencies;
Combination humoral and cellular immunity deficiencies, which account for about 20% of primary immunodeficiencies;
This category includes Severe Combined Immunodeficiency (SCID), which causes opportunistic infections and failure to thrive in infants due to little-to-no immune function. It is serious and can be fatal unless diagnosed and treated early.
Phagocytic cell defects, which account for about 15% of primary immunodeficiencies;
Complement deficiencies, which are rare and account for 2% or less of primary deficiencies; and
(Mayo Clinic 2020; Fernandez 2019; British Society for Immunology 2017)
Secondary immunodeficiencies are more common than primary immunodeficiencies. They are acquired after the immune system is weakened by an external factor (Primary Immunodeficiency UK 2017). These causes may include:
Immunosuppressive treatments such as chemotherapy.
(British Society for Immunology 2017; Fernandez 2019)
Secondary immunodeficiencies may also affect critically ill, older or hospitalised people (Fernandez 2019).
Risk Factors for Immunodeficiency
Currently, the only known risk factor for primary immunodeficiency is having a family history of a primary immunodeficiency disorder (Mayo Clinic 2020).
Diagnosing primary immunodeficiencies
Blood tests can be used to measure if a person has a normal level of blood cells and immune system cells. They can also determine if the immune system is responding properly.
Prenatal or DNA tests may be used.
(Mayo Clinic 2020)
Symptoms and Effects of Immunodeficiency
Symptoms and effects may vary depending on the type of immunodeficiency. They can include:
Infections that are:
More frequent, persistent or harder to treat than what is typical;
Opportunistic (infections that occur more often or are more severe in immunocompromised people);
Caused by unusual bacteria, viruses, fungi or parasites.
Frequent and recurring pneumonia, bronchitis, sinus infections, ear infections, meningitis or skin infections;