Why Psoriasis Is an Autoimmune Disease

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Psoriasis is an autoimmune disease, meaning that the body's immune system turns on itself and attacks normal cells and tissues—in this case, skin cells known as keratinocytes.

Because psoriasis is caused by an immune system gone awry, it is not contagious like most skin infections. You can neither "catch" it nor "spread" it.

This article explains what autoimmune diseases are and the various immune mechanisms that lead to psoriasis. It also describes the risk factors for this autoimmune skin disease and how it is treated.


6 Myths About Psoriasis

Psoriasis and the Immune System

If you have an autoimmune disease, your immune system responds abnormally to a body part, such as the skin, a joint, or the intestine. Psoriasis is one example of at least 28 diseases classified as autoimmune and possibly up to 150 in total, according to the National Institutes of Health.

The immune system is meant to defend the body against foreign invaders. But with psoriasis, the immune system regards skin cells as foreign and mounts an assault in the form of targeted inflammation.

With an autoimmune disease, there are several "players" involved in the abnormal immune response, namely:

  • Autoantibodies: Normally, the immune system will produce proteins called antibodies that recognize and "tag" foreign invaders for destruction. With an autoimmune disease, the immune system produces autoantibodies that "tag" normal cells for destruction.
  • Antigens: Every antibody is produced to match a protein on the surface of a cell, called an antigen, which it binds to. With an autoimmune disease, the antigen of a normal cell is targeted. Because normal cells are not neutralized in the way that most infections are, the attack will continue unabated, leading to chronic (persistent or recurrent) disease.
  • Lymphocytes: These are white blood cells, specifically known as T-cell lymphocytes and B-cell lymphocytes, that are central to the body's immune response. When an autoantibody "tags" a normal cell for destruction, these cells coordinate the immune assault, exposing the "invader" to inflammation to kill it. Inflammation is the body's natural response to all infections and injuries.

Under normal circumstances, skin cells turn over at a steady rate so that old cells can be shed from the surface of the skin (called the epidermis) and replaced with new ones. With psoriasis, the inflammatory autoimmune assault causes skin cells to turn over at a vastly accelerated rate.

Keratinocytes are the most abundant of all skin cells. When these are exposed to autoimmune inflammation, the turnover rate will increase from the normal to 28 to 30 days to a mere 3 to 5 days.

When this happens, skin cells will start to pile up on the surface of the skin and become compressed rather than being shed. This causes the red, scaly, itchy patches recognized as plaques. Plaques most commonly develop on the back of the forearms, shins, navel area, and scalp (although any body part can be affected).

Plaque psoriasis is the most common type of psoriasis, accounting for more than 90% of cases. Less common types include pustular psoriasis (which causes pus-filled lesions), guttate psoriasis (which causes drop-shaped lesions), and inverse psoriasis (which affect skin folds).

What Causes Psoriasis?

The cause of psoriasis is unknown. Both genetic and environmental factors are believed to play a role in the onset of the disease.

The theory is genetics, either inherited from your parents or acquired later in life, can predispose a person to the disease. Thereafter, exposure to one or more environmental factors, such as an infection, might "confuse" the immune system and cause it to regard the antigen of a normal cell as hostile.

This can cause not only the onset of psoriasis symptoms but also episodic exacerbations (flare-ups).

Risk factors linked to the onset and/or exacerbation of psoriasis include:

How Psoriasis Is Treated

Psoriasis treatment is primarily focused on calming the overreactive immune response. At the same time, an effort is made to avoid triggers that cause flare-ups and to minimize symptoms by protecting the skin barrier.

Depending on the severity of symptoms and type of psoriasis involved, the treatment may include some or all of the following:

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. National Academies of Sciences, Engineering and Medicine. Assessment of NIH research on autoimmune diseases.

  3. Rosenblum MD, Remedio KA, Abbas AK. Mechanisms of human autoimmunity. J Clin Invest. 2015 Jun 1;125(6):2228–33. doi:10.1172/JCI78088

  4. Kim W, Jerome D, Yeung J. Diagnosis and management of psoriasis. Can Fam Physician. 2017 Apr;63(4):278-85.

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By Rosalyn Carson-DeWitt, MD
Rosalyn Carson-DeWitt, MD is a medical writer, editor, and consultant.