Immunodeficiency means part of the immune system is missing or not working, so infections come too often, last too long or are caused by unusual germs. It can be primary, from inherited defects in antibodies, T cells, phagocytes or complement, or secondary to HIV, chemotherapy, steroids, malnutrition or cancer.
Key symptoms
- Ear, sinus or lung infections that keep coming back
- Infections that need IV antibiotics or do not clear with usual treatment
- Unusual infections such as thrush, Pneumocystis or deep abscesses
- Chronic diarrhea and poor weight gain in children
- Family history of immune disease or early deaths from infection
What you find on exam
- Growth and weight; signs of malnutrition
- Absent or very small tonsils and lymph nodes in antibody defects
- Thrush, skin abscesses, eczema or scarred eardrums
- Lung findings from bronchiectasis: crackles, clubbing
Tests
- Blood count with differential, including the lymphocyte count
- Immunoglobulin levels (IgG, IgA, IgM) and vaccine antibody responses
- HIV test and review of drugs that suppress immunity
- Lymphocyte subsets (flow cytometry), complement (CH50) and neutrophil function tests as needed
Treatment basics
- Treat each infection early and fully, guided by cultures
- Immunoglobulin replacement (IV or subcutaneous) for antibody deficiency
- Prophylactic antibiotics such as trimethoprim-sulfamethoxazole when indicated
- No live vaccines in significant T cell or combined defects; give inactivated vaccines
- Treat the cause in secondary disease; stem cell transplant for severe combined immunodeficiency
Red flags
- Fever with low neutrophils or signs of sepsis
- Pneumonia with low oxygen or unusual organisms
- Infant with poor growth, chronic diarrhea and severe infections
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.