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Pemphigus is an autoimmune disorder. If you have it, your immune system attacks healthy cells in your skin and mouth, causing blisters and sores. No one knows the cause. Pemphigus does not spread from person to person. It does not appear to be inherited. But some people's genes put them more at risk for pemphigus.

Pemphigoid is also an autoimmune skin disease. It leads to deep blisters that do not break easily. Pemphigoid is most common in older adults and may be fatal for older, sick patients.

Doctors diagnose pemphigus with a physical exam, a biopsy, and blood tests. The treatment of pemphigus and pemphigoid is the same: one or more medicines to control symptoms. These may include:

• Steroids, which reduce inflammation
• Drugs that suppress the immune system response
• Antibiotics to treat associated infections

NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases

Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.

When germs such as bacteria or viruses invade your body, they attack and multiply. This is called an infection. The infection causes the disease that makes you sick. Your immune system protects you from the disease by fighting off the germs.

The immune system has many different parts, including:

• Your skin, which can help prevent germs from getting into the body
• Mucous membranes, which are the moist, inner linings of some organs and body cavities. They make mucus and other substances which can trap and fight germs.
• White blood cells, which fight germs
• Organs and tissues of the lymph system, such as the thymus, spleen, tonsils, lymph nodes, lymph vessels, and bone marrow. They produce, store, and carry white blood cells.

Your immune system defends your body against substances it sees as harmful or foreign. These substances are called antigens. They may be germs such as bacteria and viruses. They might be chemicals or toxins. They could also be cells that are damaged from things like cancer or sunburn.

When your immune system recognizes an antigen, it attacks it. This is called an immune response. Part of this response is to make antibodies. Antibodies are proteins that work to attack, weaken, and destroy antigens. Your body also makes other cells to fight the antigen.

Afterwards, your immune system remembers the antigen. If it sees the antigen again, it can recognize it. It will quickly send out the right antibodies, so in most cases, you don't get sick. This protection against a certain disease is called immunity.

There are three different types of immunity:

• Innate immunity is the protection that you are born with. It is your body's first line of defense. It includes barriers such as the skin and mucous membranes. They keep harmful substances from entering the body. It also includes some cells and chemicals which can attack foreign substances.
• Active immunity, also called adaptive immunity, develops when you are infected with or vaccinated against a foreign substance. Active immunity is usually long-lasting. For many diseases, it can last your entire life.
• Passive immunity happens when you receive antibodies to a disease instead of making them through your own immune system. For example, newborn babies have antibodies from their mothers. People can also get passive immunity through blood products that contain antibodies. This kind of immunity gives you protection right away. But it only lasts a few weeks or months.

Sometimes a person may have an immune response even though there is no real threat. This can lead to problems such as allergies, asthma, and autoimmune diseases. If you have an autoimmune disease, your immune system attacks healthy cells in your body by mistake.

Other immune system problems happen when your immune system does not work correctly. These problems include immunodeficiency diseases. If you have an immunodeficiency disease, you get sick more often. Your infections may last longer and can be more serious and harder to treat. They are often genetic disorders.

There are other diseases that can affect your immune system. For example, HIV is a virus that harms your immune system by destroying your white blood cells. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome). People with AIDS have badly damaged immune systems. They get an increasing number of severe illnesses.

Kaposi sarcoma, sometimes called KS, is a type of cancer. It causes lesions (abnormal tissue) to grow in different parts of the body, including:

• The skin
• Lymph nodes
• Mucous membranes (the lining of the mouth, nose, and throat)
• Other organs

These lesions are usually red or purple. They are made of cancer cells, new blood vessels, and blood cells. The lesions may begin in more than one place in the body at the same time. This makes Kaposi sarcoma different from other cancers.

Kaposi sarcoma is caused by infection with human herpesvirus-8 (HHV-8). This virus is also called Kaposi sarcoma-associated herpesvirus (KSHV). Most people infected with this virus don't get Kaposi sarcoma. But certain people who get this virus are more likely to develop one of the types of Kaposi sarcoma:

• People with weakened immune systems due to HIV can develop epidemic (HIV-associated) Kaposi sarcoma.
• People with weakened immune systems due to medicines they need to take after an organ transplant can develop iatrogenic (transplant-related) Kaposi sarcoma.
• Older men of Mediterranean or Eastern European Jewish heritage can develop classic Kaposi sarcoma.
• Young men in Africa can develop endemic (African) Kaposi sarcoma.

Kaposi sarcoma usually starts out as one or more red, purple, or brown skin lesions on the legs and feet. They are most often on the ankles or soles of the feet. Over time, lesions may form in other parts of the body. The lesions may not cause symptoms. But sometimes the lesions can cause problems, especially as you get more of them and they grow bigger. For example:

• Pressure from the lesions may block the flow of lymph and blood in the legs and cause painful swelling
• If lesions grow in your stomach or intestines, they can bleed and may cause abdominal (belly) pain and diarrhea
• Lesions in the lungs can also bleed and may cause shortness of breath

To find out whether you have Kaposi sarcoma, your health care provider:

• Will ask about your medical and family history
• Will do a physical exam
• May order a chest x-ray to look for Kaposi sarcoma in the lungs
• May do a biopsy to check for Kaposi sarcoma lesions in the skin
• May do an endoscopy to check for Kaposi sarcoma in the stomach and intestines
• May do a bronchoscopy to check for Kaposi sarcoma in the lungs

If you do have Kaposi sarcoma, you will likely need blood and imaging tests to find out if the cancer has spread to other parts of the body.

Which treatment(s) you get will depend on

• The type of Kaposi sarcoma you have
• How many lesions you have and where in the body they are
• What kinds of problems the lesions are causing
• Your overall health

For people who have epidemic (HIV-associated) Kaposi sarcoma, taking HIV medicines may be enough to treat the Kaposi sarcoma. For people who have iatrogenic (transplant-related) Kaposi sarcoma, changing the dose of the medicines or switching medicines may be helpful. But some people with these types of Kaposi sarcoma will need additional treatment.

The treatment options for Kaposi sarcoma may include:

• Radiation therapy
• Surgery
• Cryosurgery, a treatment that uses an instrument to freeze and destroy abnormal tissue
• Chemotherapy
• Immunotherapy

NIH: National Cancer Institute