There are several different types of psoriasis:
This is the most common type of psoriasis. It typically appears as thick, flaky patches of skin on one or more parts of the body. Sometimes the patches of affected skin are large, extending over much of the body. The patches, known as plaques or lesions, can wax and wane but tend to be chronic.
Plaque psoriasis can occur anywhere on the body. Commonly affected sites are the elbows, knees, knuckles, scalp, trunk, arms and legs, and external sex organs. The plaques do not always itch, but when scratched they can become inflamed. This is known as the Koebner phenomenon.
This type of psoriasis most often affects children and young adults. It appears as small, red bumps-the size of drops of water-on the skin. It usually appears suddenly, often several weeks after an infection such as strep throat.
In adults who have plaque psoriasis, the appearance of the small droplike bumps of guttate psoriasis can be a sign that the disease is flaring up.
- Psoriasis that affects the scalp is called seborrheic psoriasis. The scalp may be the first site to be affected by psoriasis. The condition may resemble severe dandruff. Patches of thick, flaky skin may extend to the forehead below the hairline. Scales may build up in the outer ear. Other than the forehead and the ears, the face is usually spared. However, some people may have patches of inflamed skin that resemble seborrheic
dermatitis, a type of dandruff eczemathat affects the scalp and face.
- Psoriasis can affect the connective tissue that forms the nails. Pitting of the nails may be an early sign of nail psoriasis, although pitting can also occur in other diseases. Other signs of nail psoriasis include the appearance of dark spots resembling oil droplets on the nails, the build-up of flaky skin cells under the nails, and separation or loosening of the nails from their beds (onycholysis). One or more nails may be affected.
- Psoriasis that affects the palms of the hands and the soles of the feet is called palmoplantar psoriasis. It may appear as chronic flaky patches that crack and bleed. The nails may be affected as well. In severe cases the condition can be disabling.
The palms and soles can also be affected by pustular psoriasis. In this condition small, deep, pus-filled blisters appear on the palms and soles. They may have a copper-colored hue on a background of red, flaky skin. This condition may also be called palmoplantar pustulosis or acropustulosis.
- Red, flaking, thickened skin that covers most of body is called erythroderma. When this happens in a person who has a history of plaque psoriasis, it is called erythrodermic psoriasis. Other causes of erythroderma include widespread eczema (an inflammatory condtion of the skin characterized by redness, itching and oozing lesions), skin reactions to drugs, and a type of skin cancer called cutaneous
lymphoma. People with erythroderma may have fever and chills, and may need to be treated in the hospital.
- A rare and severe form of psoriasis in which small, pus-filled blisters appear on the skin is called pustular psoriasis. People with this condition may need to be treated in the hospital. They are usually ill with fever and chills. They need special therapies because standard treatments for psoriasis easily irritate their skin. Pustular psoriasis can be disabling when it affects the palms of the hands and soles of the feet.
- Psoriasis that affects areas of the body where the skin folds, such as the armpits, groin, and webs of the toes, is called inverse psoriasis or flexural psoriasis. This type of psoriasis is often white in color, appears softened as if soaked by water, and may resemble a fungal infection.