12.2 Secondary immunodeficiencies

Secondary immunodeficiencies are acquired conditions that weaken the immune system after birth. They can be caused by infections, malnutrition, medications, chronic diseases, aging, stress, and environmental factors. These conditions impact the body's ability to fight off pathogens effectively.

Diagnosing secondary immunodeficiencies involves looking for recurrent infections and running specific tests. Management focuses on treating the underlying cause, preventing infections, and providing supportive care. Regular monitoring and patient education are crucial for optimal outcomes.

Causes and Characteristics of Secondary Immunodeficiencies

Causes of secondary immunodeficiencies

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• Secondary immunodeficiencies arise after birth due to external factors impair immune system function
• Infections weaken immune response (HIV/AIDS, measles, Epstein-Barr virus)
• Malnutrition compromises immune cell production and function (protein-energy malnutrition, zinc deficiency)
• Immunosuppressive therapies intentionally dampen immune responses (corticosteroids, chemotherapy)
• Chronic diseases gradually impair immunity (diabetes, kidney disease)
• Aging naturally decreases immune system effectiveness
• Stress hormones suppress immune function
• Environmental factors damage immune cells (pollution, toxins)

Impact of diseases on immunity

• HIV/AIDS depletes CD4+ T cells severely impairs cellular immunity increases opportunistic infections
• Cancer suppresses immunity through malignancy and treatment-induced neutropenia and lymphopenia
• Diabetes mellitus impairs neutrophil function and T cell proliferation
• Chronic kidney disease causes uremia-induced immune dysfunction impairs phagocytosis and T cell activation
• Splenectomy reduces ability to clear encapsulated bacteria (Streptococcus pneumoniae) increases sepsis risk
• Severe burns compromise skin barrier trigger systemic immune suppression
• Alcoholism impairs neutrophil function reduces cytokine production

Clinical Aspects and Management of Secondary Immunodeficiencies

Diagnosis of secondary immunodeficiencies

• Recurrent infections lasting longer than normal often with opportunistic pathogens (Pneumocystis jirovecii)
• HIV/AIDS diagnosis CD4+ T cell count drops below 200 cells/μL presence of AIDS-defining illnesses (Kaposi's sarcoma)
• Drug-induced immunosuppression correlates medication use with infection onset
• Malnutrition-related immunodeficiency assessed through body mass index and serum protein levels
• Diagnostic tests include:
  1. Complete blood count with differential
  2. Immunoglobulin level measurement
  3. Lymphocyte subset analysis
  4. Delayed-type hypersensitivity skin tests
  5. Vaccine response assessment

Management of immunodeficiency patients

• Treat underlying cause when possible (antiretroviral therapy for HIV)
• Prevent infections through vaccination prophylactic antibiotics good hygiene
• Manage complications provide supportive care (nutritional support, IVIG therapy)
• Disease-specific approaches (glycemic control for diabetes)
• Regular monitoring of immune function screen for opportunistic infections
• Patient education on medication adherence symptom recognition infection risk reduction
• Adjust treatment based on clinical response and immune function assessments