Acquired Immune Deficiencies

Causes

• Infections:
  • Human Immunodeficiency Virus (HIV): The most well-known cause. HIV attacks and destroys CD4+ T cells, which are crucial for immune function, leading to Acquired Immunodeficiency Syndrome (AIDS) in its advanced stages.
  • Other viral infections: Some viruses (e.g., Epstein-Barr virus, cytomegalovirus, measles) can temporarily suppress the immune system.
  • Severe bacterial or fungal infections: Can overwhelm and exhaust the immune system.
• Malnutrition: Severe deficiencies in protein, vitamins (e.g., A, C, D, B vitamins), and minerals (e.g., zinc, selenium) can significantly impair immune function.
• Cancers:
  • Cancers of the immune system: Leukemias, lymphomas, and multiple myeloma directly affect the production and function of immune cells.
  • Other cancers: Advanced cancers can weaken the immune system.
• Medical Treatments:
  • Chemotherapy and Radiation Therapy: Used in cancer treatment, these therapies kill rapidly dividing cells, including immune cells in the bone marrow.
  • Immunosuppressive medications: Used to prevent organ transplant rejection or treat autoimmune diseases (e.g., corticosteroids, biologics like TNF inhibitors) intentionally suppress the immune system.
• Chronic Diseases:
  • Kidney failure (uremia): Impairs immune cell function.
  • Diabetes: Can lead to impaired neutrophil function and increased infection risk.
  • Liver disease (cirrhosis): Affects the production of immune proteins and can lead to immune dysfunction.
• Autoimmune Disorders: While some autoimmune diseases involve an overactive immune response, the chronic inflammation and treatments used can sometimes lead to a secondary immunodeficiency.
• Splenectomy (removal of the spleen): The spleen plays a vital role in filtering blood and producing immune cells, so its removal increases susceptibility to certain bacterial infections.
• Aging: The immune system naturally becomes less effective with age (immunosenescence), making older adults more susceptible to infections and less responsive to vaccines.

Symptoms

• Frequent and recurrent infections: Such as pneumonia, bronchitis, sinusitis, ear infections, skin infections.
• Severe infections: Infections that are unusually severe or prolonged.
• Infections with unusual or opportunistic organisms: Germs that typically don't cause illness in healthy individuals.
• Poor response to standard antibiotic treatment.
• Slow wound healing.
• Persistent fatigue.
• Unexplained weight loss.
• Swollen lymph nodes.
• Other symptoms related to the underlying cause: (e.g., fever, night sweats, diarrhea, skin rashes in HIV/AIDS; symptoms of cancer or chronic organ disease).

Diagnosis

• Medical history and physical exam: The doctor will ask about recurrent infections, family history, lifestyle, and any underlying medical conditions or medications.
• Blood tests:
  • Complete Blood Count (CBC) with differential: To count white blood cells (including lymphocytes, neutrophils), red blood cells, and platelets.
  • Immunoglobulin levels (IgG, IgA, IgM): To measure the levels of different types of antibodies.
  • Lymphocyte subsets: To count specific types of immune cells, such as CD4+ T cells (especially for HIV).
  • Antibody response to vaccines: To assess how well the immune system produces antibodies after vaccination.
  • Tests for specific infections: (e.g., HIV test, hepatitis tests).
  • Tests for underlying conditions: (e.g., blood glucose for diabetes, kidney/liver function tests, cancer markers).
• Bone marrow biopsy: May be performed if a primary bone marrow disorder or cancer is suspected.
• Imaging studies: (e.g., chest X-ray, CT scan) to look for infections or other abnormalities.

Treatment

• Treating the underlying cause:
  • Antiretroviral therapy (ART) for HIV: Suppresses the virus, allowing the immune system to recover.
  • Treating malnutrition: Nutritional supplements and dietary changes.
  • Cancer treatment: Chemotherapy, radiation, surgery.
  • Managing chronic diseases: (e.g., diabetes control, kidney dialysis).
  • Adjusting medications: Reducing or changing immunosuppressive drugs if possible.

• Preventing and treating infections:
  • Antibiotics, antifungals, antivirals: To treat active infections.
  • Prophylactic medications: May be prescribed to prevent infections in severely immunocompromised individuals.
  • Vaccinations: Recommended for many individuals, though response may be reduced. Live vaccines may be contraindicated.
  • Good hygiene: Frequent handwashing, food safety.
• Immune support therapies:
• • Intravenous Immunoglobulin (IVIg) or Subcutaneous Immunoglobulin (SCIg): For individuals with severe antibody deficiencies, providing ready-made antibodies to fight infections.
  • Granulocyte colony-stimulating factors (G-CSF): To stimulate neutrophil production in some cases of neutropenia.
  • Stem cell transplantation: For severe cases of bone marrow failure or certain cancers.

Living Safely With a Weakened Immune System

A weakened immune system changes what an ordinary fever means, which vaccines are safe, and which everyday exposures matter, whether the cause is HIV, a medication, a blood cancer, or a failing organ. What follows are the parts that apply most often.

HIV: the test everyone should have once, and treatment that works

Every adult is screened for HIV at least once, because many infections are found late and treatment is now a single daily tablet such as bictegravir-emtricitabine-tenofovir or a dolutegravir-based combination that restores immune function and, once the virus is undetectable, prevents sexual transmission. Tenofovir-emtricitabine taken as prevention protects people at ongoing risk. Hepatitis screening travels with the HIV test; see our hepatitis C screening article.

Medications that count as immunosuppression

Prednisone at 20 mg a day or more for two weeks or longer, methotrexate, and biologics such as adalimumab all reduce immune defenses enough to change vaccine and infection advice. Anyone starting them is screened for tuberculosis and hepatitis B first and brought up to date on vaccines. Tell every clinician and pharmacist which of these you take.

Vaccines: which are safe, which are not

Inactivated and recombinant vaccines are safe and more important than usual: annual influenza, updated COVID-19, pneumococcal, and the recombinant shingles vaccine, which is recommended for immunocompromised adults from age 19. Live vaccines, including MMR, varicella, and the nasal flu spray, are generally avoided. Our adult vaccine checklist and pneumococcal vaccine update cover timing, and the shingles page explains why that infection is both more common and more severe with a weakened immune system.

Florida-specific exposures

Raw oysters and other raw shellfish from Gulf waters carry Vibrio vulnificus, which is far more dangerous in people with immune suppression or liver disease, and the same bacteria enters through open cuts in warm seawater; our Vibrio safety article covers both. Gardening soil, standing water after storms, and undercooked food are the other common sources here; handwashing and food safety do more than any supplement.

When a fever is an emergency

A fever with a low neutrophil count, whether from chemotherapy, a blood cancer such as chronic leukemia or lymphoma, or a medication, is treated as an emergency because infection can progress within hours; the neutropenia page covers what that means. People without a spleen need urgent antibiotics for any fever. Poorly controlled diabetes and cirrhosis impair immunity more than most people realize. Our immunology team coordinates screening, vaccination, and specialist care. The CDC and MedlinePlus publish patient guidance on HIV and immune disorders.

If you take an immunosuppressing medication and are not sure your vaccines are current, or have never had an HIV test, schedule a visit.