Secondary immunodeficiencies (with the exception of AIDS)

1. Big picture

Secondary immunodeficiency means acquired immune weakness caused by another disease, treatment, nutritional state, organ failure, or anatomical loss of immune function. It is much more common than primary immunodeficiency in adults.

For the exam, the examiner usually wants three things:

1. Recognize the pattern: recurrent, severe, unusual, persistent, or opportunistic infections.
2. Find the cause: drugs, malignancy, diabetes, renal/liver failure, protein loss, malnutrition, asplenia, transplantation, burns/trauma, chronic disease.
3. Manage safely: treat infections early, reduce reversible causes, vaccinate appropriately, avoid live vaccines when contraindicated, give prophylaxis or immunoglobulin replacement when indicated.

AIDS is excluded from this topic, but HIV testing still belongs in the diagnostic workup of unexplained immunodeficiency because missing HIV would be a major clinical error.

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