Psoriasis is often referred to as an inflammatory disease and an immune-mediated disease. But is psoriasis an autoimmune disease? Health experts now believe that psoriasis and psoriatic arthritis (PsA) are autoimmune disorders.

Let’s examine what causes psoriasis and classifies it as an autoimmune disease.

What Is an Autoimmune Disease?

In an autoimmune disease, the body loses the ability to tell the difference between some of the body’s tissues and harmful microbes that can cause sickness, leading the body to attack healthy tissue. In psoriasis, you experience these attacks as a flare-up.

The immune system is made up of cells and proteins that attack anything foreign to the body, such as invading bacteria, viruses, and other potential causes of infection and sickness. The immune system is designed to attack and neutralize invaders by recognizing molecules on them known as antigens. It’s important that the immune system knows the difference between the body’s own component and a foreign invader.

However, when immune cells begin responding abnormally, they misidentify aspects of our own body as harmful invaders and attack. This abnormal response is described as being autoreactive or autoimmune — “auto” is a Greek prefix meaning “self.” The self-antigens targeted in autoimmune diseases are known as autoantigens.

Autoimmune diseases are classified by the type of tissue that is being attacked. For example, in rheumatoid arthritis, the tissue lining the inside of the joints is attacked. In type 1 diabetes, the immune system attacks and destroys insulin-producing cells in the pancreas. In celiac disease, the immune system attacks the small intestine when gluten is consumed. And in people with the skin condition psoriasis, the immune system produces inflammatory reactions against molecules related to the skin.

What Happens During Psoriasis Autoimmune Attacks?

In people with psoriasis, the immune system attacks autoantigens on structures in the skin. These autoantigens include protein products made by the skin cells. Studies have identified the presence of these autoantigens in psoriatic lesions.

Autoantigens are believed to activate T cells and other cells of the immune system. T cells can destroy tissue and produce inflammatory chemicals such as interleukin (IL)-17A that promote the abnormal growth of skin cells. Because of the role of this interleukin in inflammation, there are now drugs that work against it and are used to treat psoriasis.

Other immune cells, known as B cells, can also contribute to autoimmunity (an autoimmune response) in psoriasis. B cells produce proteins known as antibodies that can help destroy antigens. In people with psoriasis and PsA (together known as psoriatic disease), B cells make antibodies against the autoantigens associated with the skin. Antibodies made against autoantigens are referred to as autoantibodies.

Ultimately, the dysfunction and autoimmune activity of the immune system in psoriasis leads to the severe inflammation that contributes to overactive skin cell growth and psoriatic lesions or joint damage. High levels of inflammation from the overactive immune system may also be behind a higher risk for heart disease in people with psoriasis. Heart disease can be one of the comorbidities of psoriasis — that is, a disease that occurs alongside the skin condition.

Understanding the role of the immune system in psoriasis and PsA can help those living with the conditions better understand their symptoms and treatment. As researchers learn more about why and how the immune system functions abnormally in psoriasis, they may identify better and more effective treatment options for these long-term conditions.

Risk Factors for Autoimmunity

Although scientists don’t know exactly what causes autoimmunity to develop in people with the skin disease psoriasis, most believe it is a combination of environmental and genetic factors.

Psoriasis does not have a distinct pattern of inheritance, but having a family history of psoriasis increases the likelihood of a person developing the disease. Genome-wide association studies have identified certain genes associated with the development of psoriasis. These studies compare the genetic material of healthy people to people with psoriasis to identify any genes associated with the disease. Many of the genes associated with psoriasis influence the immune system.

Environmental factors such as strep throat are also associated with the development of psoriasis. Interestingly, scientists have identified T cells that attack both strep antigens and skin autoantigens. One theory is that T cells originally meant to fight the strep throat infection may accidentally cause an autoimmune reaction by also recognizing skin autoantigens.

People with one autoimmune disease are also at greater risk for developing other autoimmune conditions.

Psoriasis Treatment and Autoimmunity

The treatment of psoriasis generally focuses on reducing inflammation.

First of all, people diagnosed with psoriasis need to make some lifestyle changes and try to avoid risk factors, such as stress and smoking. Following an anti-inflammatory diet and exercising regularly can also help.

A health care provider such as a dermatologist may prescribe topical or systemic (oral or intravenous) corticosteroids. A corticosteroid is a synthetic version of the naturally occurring hormone cortisol. Corticosteroids work by reducing inflammation and suppressing the immune system. Topical (placed on the skin) steroids in the form of creams or ointments can also reduce the rate of skin growth, causing you to experience fewer symptoms like silvery scales.

Doctors may prescribe immunosuppressants, such as disease-modifying antirheumatic drugs (DMARDs). Most frequently prescribed is methotrexate, a drug that can be administered either orally or via a subcutaneous (under the skin) injection.

If your psoriasis is severe and continues despite treatment with corticosteroids or DMARDs, your doctor may prescribe injected or infused medications known as biologics. Biologic drugs are made from living cells such as bacteria, yeast, or cells from animals. These drugs usually have positive results but more severe side effects. Biologics target and block specific molecules associated with inflammation.

Examples of biologic therapies that target inflammatory substances include:

• Certolizumab pegol (Cimzia)
• Etanercept (Enbrel)
• Infliximab (Remicade)
• Secukinumab (Cosentyx)
• Ustekinumab (Stelara)

People treated with biologics need to be closely monitored and fully informed on the way of administration and side effects of the drug. Blocking inflammatory substances can reduce inflammation and ramp down the immune system.

Doctors now believe that psoriasis and PsA occur when the body’s immune system mistakenly attacks its own cells. This understanding helps them to develop approaches that directly treat this immune response, aiming for more targeted and effective care.

Talk With Others Who Understand

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