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Multiple sclerosis (although it is thought to be an immune-mediated process)

What can go wrong with your immune system?

When your immune system doesn’t work the way it should, it is called an immune system disorder. You may:

  • Be born with a weak immune system. This is called primary immune deficiency.
  • Get a disease that weakens your immune system. This is called acquired immune deficiency.
  • Have an immune system that is too active. This may happen with an allergic reaction.
  • Have an immune system that turns against you. This is called autoimmune disease.

Immune system disorders

Here are some common examples:

  • Severe combined immunodeficiency (SCID). This is an example of an immune deficiency that is present at birth. Children are in constant danger of infections from bacteria, viruses, and fungi. This disorder is sometimes called “bubble boy disease.” In the 1970s, a boy had to live in a sterile environment inside a plastic bubble. Children with SCID are missing important white blood cells.
  • Temporary acquired immune deficiencies. Your immune system can be weakened by certain medicines, for example. This can happen to people on chemotherapy or other drugs used to treat cancer. It can also happen to people following organ transplants who take medicine to prevent organ rejection. Also, infections like the flu virus, mono (mononucleosis), and measles can weaken the immune system for a brief time. Your immune system can also be weakened by smoking, alcohol, and poor nutrition.
  • AIDS. HIV, which causes AIDS, is an acquired viral infection that destroys important white blood cells and weakens the immune system. People with HIV/AIDS become seriously ill with infections that most people can fight off. These infections are called “opportunistic infections” because they take advantage of weak immune systems.