What Is Psoriasis?
Psoriasis is a common, chronic, genetic, systemic inflammatory disease that is characterized by symptoms and signs such as elevated itchy plaques of raised red skin covered with thick silvery scales. Psoriasis is usually found on the elbows, knees, and scalp but can often affect the legs, trunk, and nails. Psoriasis may be found on any part of the skin.
Is Psoriasis Contagious?
Psoriasis is not an infection and therefore is not contagious. Touching the affected skin and then touching someone else will not transmit psoriasis.
What Are Psoriasis Causes and Risk Factors?
The immune system plays a key role in psoriasis. In psoriasis, a certain subset of T lymphocytes (a type of white blood cell) abnormally trigger inflammation in the skin as well as other parts of the body. These T cells produce inflammatory chemicals that cause skin cells to multiply as well as producing changes in small skin blood vessels, resulting ultimately in elevated scaling plaque of psoriasis.
Psoriasis has a genetic basis and can be inherited. Some people carry genes that make them more likely to develop psoriasis. Just because a person has genes that would make him more likely to have psoriasis doesn't mean he will have the disease. About one-third of people with psoriasis have at least one family member with the disease. Certain factors trigger psoriasis to flare up in those who have the genes.
Environmental factors such as smoking, sunburns, streptococcal sore throat, and alcoholism may affect psoriasis by increasing the frequency of flares. Injury to the skin has been known to trigger psoriasis. For example, a skin infection, skin inflammation, or even excessive scratching can activate psoriasis. A number of medications have been shown to aggravate psoriasis.
Psoriasis flare-ups can last for weeks or months. Psoriasis can go away and then return.
Plaque psoriasis is the most common type of psoriasis and is characterized by red skin covered with silvery scales and inflammation. Plaques of psoriasis vary in shape and frequently itch or burn.
Approximately 1%-2% of people in the United States, or about 5.5 million, have plaque psoriasis. Up to 10% of people with plaque psoriasis also have psoriatic arthritis. Individuals with psoriatic arthritis have inflammation in their joints that could result in permanent joint damage if not treated aggressively. Recent information indicates that most patients with psoriasis are also predisposed to obesity, diabetes, and early cardiovascular diseases. It is now becoming apparent that psoriasis is not just a skin disease but can have widespread systemic effects.
Sometimes plaque psoriasis can evolve into more severe disease, such as pustular or erythrodermic psoriasis. In pustular psoriasis, the red areas on the skin contain small blisters filled with pus. In erythrodermic psoriasis, a wide area of red and scaling skin is typical, and it may be itchy and uncomfortable.
What Are Psoriasis Treatments?
There are many topical and systemic treatments for psoriasis, but it must be born in mind that although many of them are effective in improving the appearance of the skin disease, none of them cure the condition.
Picture of plaque psoriasis on the elbow. Plaque psoriasis is the most common type of psoriasis. Image courtesy of Hon Pak, MD. Picture of guttate psoriasis. Red drop-like lesions are found on the skin. Image courtesy of Hon Pak, MD. A close-up view of guttate psoriasis. Notice the salmon-pink (red) drop-like lesions. Fine scales can be seen on the lesions. These scales are much finer than those associated with plaque psoriasis. Image courtesy of Hon Pak, MD. Picture of plaque psoriasis with fissures, which are splits in the skin. Fissures usually occur where the skin bends (joints). The skin may bleed and is more susceptible to infection. Image courtesy of Hon Pak, MD. Picture of plaque psoriasis on the back. Image courtesy of Hon Pak, MD. Picture of severe plaque psoriasis. Note the classic red color and scales or plaque. Image courtesy of Hon Pak, MD. Picture of pustular psoriasis. Note the clearly defined, raised bumps on the skin that are filled with pus (pustules). The skin under and around these bumps is reddish. Image courtesy of Hon Pak, MD. Picture of palmoplantar pustular psoriasis, a type of pustular psoriasis that appears on the palms of the hands or the soles of the feet. Image courtesy of Hon Pak, MD.
Psoriasis causes the top layer of skin cells to become inflamed and grow too quickly and flake off.
Boehncke, Wolf-Henning, and Schön, Michael. "Psoriasis." Lancet May 27, 2015: 1-12.
Menter, Alan, et al. "Guidelines of Care for the Management of Psoriasis and Psoriatic Arthritis." J Am Acad Dermatol May 2008: 826-850.
Weigle, Nancy, and Sarah McBane. "Psoriasis." Am Fam Physician. 87.9 (2013): 626-633.