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Causes, Risk Factors and Prevention of Psoriasis

By Cynthia Price, M.D. ; Updated August 14, 2017

With normal, unaffected skin, the body takes 28 to 30 days to create new skin cells and shed dead ones. But when you have plaque psoriasis, your immune system is overactive, causing skin cells to be pushed to the skin’s surface in approximately three to four days.

However, your body can’t keep up with this rate of production. So while new skin cells are being produced, dead skin cells pile up on top of each other. This creates thick, red, itchy, flaky patches known as plaques.

The Role of Genetics

Psoriasis occurs in increased frequency in some families. When it comes to children developing psoriasis, a large German survey found that if both parents were affected with psoriasis, the risk for the child developing the disorder was up to 50 percent. But if only one parent was affected, the risk was 16 percent. Likewise, if one sibling was affected, the risk was 8 percent.

Based upon the analysis of family pedigrees, a polygenic (or one that involves many genes) inheritance provides the best model for the complex genetics of psoriasis. There’s also evidence that genetic factors play a role in the clinical course or psoriasis. The PSOR1 gene is considered a major gene that’s involved in up to 50 percent of patients with psoriasis.

Psoriasis as an Autoimmune Disease

Autoimmune diseases occur when the body’s immune system accidentally attacks and destroys healthy body tissue. There are more than 80 types of autoimmune diseases, including plaque psoriasis.

In psoriasis patients, the T cells attack healthy skin cells. They trigger an immune response that leads to blood vessel dilation in the skin around the plaques and an increase in white blood cells in the outer layer of skin.

This results in an increased production of healthy skin cells, T cells and white blood cells. The ongoing cascade of new skin cells moves to the outermost layer in days rather than weeks. Dead skin and white blood cells do not slough off quickly enough and therefore build up into thick, scaly patches on the skin’s surface.

Potential Triggers

Triggering factors can be both external (those that directly interact with the skin) and internal or systemic, which can elicit psoriasis in genetically predisposed patients. Here are a few of the most common:

1. Stress

Additionally, environmental factors, including infection, drugs, trauma, weather changes, obesity and stress, play an important role in the development of psoriasis. Severe emotional stress tends to aggravate psoriasis in almost half of those patients studied.

Exacerbations of psoriasis typically occur a few weeks to months after a stressful life event. Additionally, in pregnancy, psoriasis symptoms can improve. However, after childbirth, there’s a tendency for it to get worse.

2. Alcohol Consumption, Smoking and Obesity

Obesity, alcohol consumption and smoking have also been associated with psoriasis. Smoking plays a role in the onset of psoriasis, while obesity appears to be a result of psoriasis.

The relationship between alcoholism and psoriasis is likely due to the psychological effects of the patient and psoriasis. And excess weight increases the risk of psoriasis, as plaques often develop in skin folds.

3. Infections

Infections, particularly bacterial, may induce or flare psoriasis. This has been observed in approximately 45 percent of psoriatic patients. Beta-hemolytic strep, especially manifesting as strep throat, is the most common offender.

Additionally, dental abscesses, perianal cellulitis and impetigo can flare psoriasis. These types of infections typically manifest themselves in the form of “gumdrop” psoriasis. This type of psoriasis is common in childhood and teenagers. Similarly, patients with HIV have higher rates of psoriasis. Less commonly, sinus, respiratory, gastrointestinal or genitourinary tracts may be responsible for disease flare.

4. Skin Trauma

Trauma to the skin like a scrape, bite or sunburn can trigger psoriasis. This is called the Koebner phenomenon. It is observed in approximately 25 percent of patients with psoriasis. Other forms of skin injuries, such as sunburn, drug eruptions or viral rashes, can also induce psoriasis. The lag time between the trauma and the appearance of the skin lesion is usually two to six weeks.

5. Certain Drugs

There are several drugs that induce psoriasis, including: lithium (used to treat bipolar disease), interferon (used for immune system regulation), beta blockers and calcium channel blockers (used for hypertension), terbinafine (used for fungal infections) and anti-malarials (used to treat infection and for autoimmune diseases).

Rapid tapers of oral steroids (prednisone) may induce pustular psoriasis as well as flares of plaque psoriasis. That is why it is very important to be aware of the affects of these medications on one’s psoriasis before starting any of them.

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