Any disease or treatment that prevents the body's immune system from working normally can cause immune system deficiency.

The most common causes for immune system deficiency include:

• AIDS
• Chemotherapy:
• The administration of medicines that kill cancer cells.
• Diabetes
• Medication therapy after an organ transplant

Additional conditions that can prevent the immune system from working normally include:

• Adrenal insufficiency
• Elderly
• Anemia
• Cancer:
• Leukemia
• Lymphoma
• Metastatic cancer
• Cirrhosis
• Congestive heart failure
• Cushing's disease
• Cystic fibrosis
• Endocarditis
• Hepatitis B
• Hepatitis C
• Kidney failure
• Malnutrition
• Radiation therapy:
• Exposing cancer cells to radiation can kill them.
• Severe infections
• Pneumonia
• Urinary tract infections
• Sepsis
• Sickle cell anemia
• Splenectomy
• Steroid medications:
• Prednisone
• Medrol