Psoriasis is the most prevalent autoimmune disease in the U.S. It is estimated to affect 2-2.6% of the U.S. population, or as many as 7.5 million Americans. It affects men and women at about the same rate and is more prevalent in Caucasians. Children are also affected. Up to 30% of people diagnosed with psoriasis may subsequently develop psoriatic arthritis, a potentially debilitating joint condition.
It is believed that approximately 10% of the general population inherits one or more of the genes that predispose them to develop psoriasis, but only 2-3% develops the disease in response to “triggers” that include stress, injury (including severe sunburn), some prescription medications and infection. Although scientifically unproven, some people with psoriasis suspect that allergies, diet and weather trigger their psoriasis. Strep infection is known to trigger guttate psoriasis (see description below).
Psoriasis can occur on any part of the body — eyelids, ears, mouth and lips, skin folds, hands and feet, arms and legs, torso and nails. The skin at each of these sites is different and requires different treatments. The most common form, plaque psoriasis, appears most often as red, scaly patches that itch and bleed. Psoriasis is chronic, painful and disfiguring. It is sometimes associated with other serious health conditions, including diabetes, heart disease and depression.
There are five distinct types of psoriasis:
- Plaque Psoriasis (psoriasis vulagaris)
About 80% percent of patients have plaque psoriasis. It is characterized by raised, inflamed, red lesions covered by silvery white scales. It is typically found on the elbows, knees, scalp and lower back.
- Guttate Psoriasis
A form of psoriasis that often starts in childhood or young adulthood. It appears as small, red, individual spots on the skin, usually the trunk and limbs. Known triggers include strep throat, upper respiratory infections, tonsillitis, stress, injury to the skin and some prescriptions drugs (antimalarials and beta-blockers).
- Inverse Psoriasis
Found in the armpits, groin, under the breasts, and in other skin folds around the genitals and the buttocks. This type of psoriasis appears as bright-red lesions that are smooth and shiny. Inverse psoriasis is subject to irritation from rubbing and sweating because of its location. It can be more troublesome in overweight people or those with deep skin folds.
- Pustular Psoriasis
Primarily seen in adults, pustular psoriasis is characterized by white blisters of non-infectious pus (consisting of white blood cells) surrounded by red skin. The blisters may be localized to certain areas of the body, such as the hands and feet, or cover most of the body. It begins with the reddening of the skin followed by formation of pustules and scaling. Pustular psoriasis may be triggered by some prescription medications or topical agents, overexposure to UV light, pregnancy, systemic steroids or infection.
- Erythrodermic Psoriasis
A particularly inflammatory form of psoriasis that affects most of the body surface. It is characterized by periodic, widespread, fiery redness of the skin and the shedding of scales in sheets, rather than smaller flakes. The reddening and shedding of the skin are often accompanied by severe itching and pain, heart rate increase and fluctuating body temperature. Erythrodermic psoriasis causes protein and fluid loss that can lead to severe illness, including infection, pneumonia and congestive heart failure. Known triggers include the abrupt withdrawal of a systemic psoriasis treatment including cortisone, allergic reaction to a drug (Koebner response), severe sunburns, infection and medications such as lithium, anti-malarial drugs and strong coal-tar products.
Psoriasis triggers include:
Stress can cause psoriasis to flare for the first time or aggravate existing psoriasis. Relaxation and stress reduction may help.
- Injury to skin
Psoriasis can appear in areas of the skin that have been injured or traumatized, a phenomenon called the Koebner [KEB-ner] response. Vaccinations, sunburns and scratches can all trigger a Koebner response (treatable when caught early).
Medications associated with triggering psoriasis including lithium, antimalarials (Plaquenil, Quinacrine, chloroquine and hydroxychloroquine), Inderal, Quinidine and Indomethacin.
A diagnosis of psoriasis is usually based on the appearance of the skin; there are no special blood tests or diagnostic procedures. A skin biopsy (or scraping) is often used to rule out other disorders and confirm the diagnosis. Treatment options most often include topical agents for mild disease, phototherapy for moderate disease and prescription oral and injected medication for severe disease.