secondary immunodeficiency
Summary
Secondary immunodeficiency is acquired impairment of immune function due to external factors, in contrast to primary (congenital) immunodeficiencies. Most commonly caused by HIV infection, but also results from malnutrition, medications, malignancies, or chronic diseases. These patients have increased susceptibility to opportunistic infections and certain cancers.
Detail
Secondary immunodeficiency represents acquired dysfunction of the immune system due to environmental, infectious, pharmacological, or pathological causes. The most prominent example is HIV infection, which specifically targets CD4+ T helper cells, leading to progressive immune deterioration and AIDS when CD4+ count falls below 200 cells/μL. Other major causes include immunosuppressive medications (corticosteroids, chemotherapy, transplant drugs), malnutrition (particularly protein-energy malnutrition affecting antibody production), hematologic malignancies (leukemia, lymphoma), chronic kidney or liver disease, diabetes mellitus, and advanced age. The clinical presentation varies based on which immune components are affected: humoral defects increase bacterial infections, cellular defects predispose to viral/fungal/mycobacterial infections, and combined defects create vulnerability to opportunistic pathogens. Unlike primary immunodeficiencies, secondary forms are often reversible if the underlying cause is addressed. Diagnosis involves assessing immune function through complete blood count with differential, immunoglobulin levels, and specific tests like CD4+ counts in HIV patients.
Sources
- Abbas, Lichtman & Pillai - Cellular and Molecular Immunology
- Kumar, Abbas & Aster - Robbins Basic Pathology
- Janeway's Immunobiology
- First Aid for the USMLE Step 1
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