The Massachusetts General Hospital describes psoriasis as a long-lasting skin condition in which patches of skin become inflamed, red, raised and scaly. Psoriasis is a very common skin condition, affecting an estimated 7.5 million people in the United States. The American College of Dermatology reports that the specific cause of psoriasis is unknown, but scientists think the cause is related to the immune system. There are several different types of psoriasis that have distinct signs and symptoms.
Plaque Psoriasis
Plaque psoriasis is the most common form of psoriasis, according to the Mayo Clinic, and it causes patches of red, dry, raised skin that are called plaques. The plaques are eventually covered with silver-colored scales, and can be itchy and painful. Plaque psoriasis can appear on skin anywhere on the body, including inside the mouth or on the genitals. The American Academy of Dermatology notes, however, that more common sites of plaque formation are the elbows, knees, scalp, and lower back.
Guttate Psoriasis
This type of psoriasis commonly affects children, according to the Massachusetts General Hospital. Guttate psoriasis usually starts with a sore throat, followed by the appearance of small patches of raised, red skin. The American Academy of Dermatology adds that this the rash usually clears up within weeks or months.
Pustular Psoriasis
Pustular psoriasis causes the formation of white pustules with surrounding red skin, according to the American Academy of Dermatology. The usual form of pustular psoriasis is localized, meaning that the pustules develop only on certain areas of the body. A very severe form of this condition is called generalized pustular psoriasis, in which pustules form on the skin all over the body. This form is very rare, but may be fatal.
Erythrodermic Psoriasis
The Mayo Clinic reports that erythrodermic psoriasis is the most rare form of psoriasis. A red and peeling rash that affects the skin, sometimes over the entire body, characterizes this form of psoriasis. The American Academy of Dermatology adds that the red rash can itch severely, and be quite painful. This is a severe condition, and may be life-threatening.
Inverse Psoriasis
Inverse psoriasis usually affects areas of skin that provide a warm, moist, dark environment, such as the armpits, under the breasts, and surrounding the genitals, according to the Mayo Clinic. This condition involves the development of patches of red, inflamed, and smooth skin. Friction and sweating exacerbate this form of psoriasis, which is more common in people who are overweight.
