The skin lesions seen in psoriasis may vary in severity from minor localized patches to complete body coverage.
Psoriasis changes the life cycle of skin cells. The dry scales are thought to result from the rapid proliferation of skin cells triggered by the release of inflammatory chemicals, when the immune system mistakes a normal skin cell for a pathogen.
Psoriasis frequently occur on the skin of the elbows, knees, and scalp, but can affect any area, including the palms of hands, soles of feet, genitals, and in areas of friction. Fingernails and toenails are also frequently affected.
An inflammatory, destructive form of arthritis (inflammation of the joints), known as psoriatic arthritis, affects about 10%-35% of individuals with psoriasis. The joints of the hands, knees, and ankles tend to be most commonly affected.
Psoriasis has a variable course, periodically improving and worsening. Many people note a worsening of their symptoms in the colder winter months.
Psoriasis is estimated to affect approximately 1%-3% of the U.S. population. It currently affects roughly 7.5 million to 8.5 million people in the U.S.
The types of psoriasis include the following:
- Plaque Psoriasis - This form of psoriasis typically manifests as red and white scaly patches on the top layer of the skin. It is the most common form of psoriasis.
- Guttate Psoriasis - This type of psoriasis can start in childhood or young adulthood, and typically manifests as small, drop-like spots.
- Inverse Psoriasis - This type of psoriasis causes red lesions in body folds like of the underarms, navel, groin, and buttocks
- Nail psoriasis - This type of psoriasis can affect fingernails and toenails, causing pitting, abnormal nail growth and discoloration.
- Pustular Psoriasis - This type causes small pus-filled yellowish blisters.
- Erythrodermic Psoriasis - This rare inflammatory type of psoriasis can develop over the entire body.
Health risks associated with psoriasis
Psoriasis has been associated with an increased risk of certain cancers, diabetes, arthritis, cardiovascular disease, and other immune-mediated disorders such as Crohn's disease and ulcerative colitis.
Causes and Triggers
Psoriasis is generally considered a genetic disease, thought to be triggered or influenced by environmental factors. It is common for psoriasis to be found in members of the same family, therefore family history is very helpful in making the diagnosis. Psoriasis typically starts or worsens because of a trigger. Trigger factors include: Infections (such as strep throat or skin infections), injury to the skin also known as the Koebner phenomenon, stress, cold weather, smoking, excessive alcohol consumption, certain medications, and withdrawal of a systemic corticosteroid.
No cure is available for psoriasis, but various treatments can help to control the symptoms:
- For mild disease that involves only small areas of the body (like less than 10% of the total skin surface), topical corticosteroids, vitamin D analogue creams (Dovonex), topical retinoids (Tazorac), moisturizers, topical immunomodulators (tacrolimus and pimecrolimus), anthralin, and coal tar, may be very effective.
- For moderate to severe disease that involves much larger areas of the body (like 20% or more of the total skin surface), topical products may not be effective or practical to apply. These situations may require ultraviolet light treatments or systemic medications like acitretin, cyclosporine, methotrexate, mycophenolate mofetil, apremilast (Otezla), and others.
- For psoriatic arthritis, systemic medications are generally required to stop the progression of permanent joint destruction.