Approach to the patient with suspected immunodeficiency

[Tariq Zaki]

Immunodeficiency typically manifests as recurrent infections. However, recurrent infections are more likely to have causes other than immunodeficiency (eg, inadequate treatment, resistant organisms, other disorders that predispose to infection). Both clinical and laboratory findings are needed for diagnosis.
(See also Overview of Immunodeficiency Disorders.)
Immunodeficiency can be

Primary: Genetically determined, typically manifesting during infancy or childhood
Secondary: Acquired

There are many causes of secondary immunodeficiency, but most immunodeficiencies result from one or more of the following:

Systemic disorders (eg, diabetes, undernutrition, HIV infection)
Immunosuppressive treatments (eg, cytotoxic chemotherapy, bone marrow ablation before transplantation, radiation therapy)
Prolonged serious illness (particularly in critically ill, older, and/or hospitalized patients)

Primary immunodeficiencies are classified by the main component of the immune system that is deficient, absent, or defective:

Humoral immunity
Cellular immunity
Combined humoral and cellular immunity
Phagocytic cells
Complement proteins