There are five different types of psoriasis:
- plaque-type psoriasis
- guttate psoriasis
- inverse psoriasis
- erythrodermic psoriasis
- pustular psoriasis
Plaque-Type Psoriasis
The most common form of psoriasis is known as plaque-type psoriasis (or psoriasis vulgaris). As previously explained, the term "plaque" is used to describe a raised area of skin that is greater than 3/8 inch (1 centimeter) in diameter. By definition, many of the areas affected are greater than that in diameter, although smaller areas of raised skin less than 3/8 inch (1 centimeter) (papules) might be present. Smaller papules may join to form a larger plaque. The affected area is usually raised, red, and scaly. The lesions are usually well defined, meaning that the border between involved skin and uninvolved skin is remarkably sharp. The lesions of psoriasis are normally round to oval in shape. Scales can appear as silvery-white and powdery, and in cases can be quite thick, even resembling an oyster shell (ostraceous).
Scales can flake or peel off in thin transparent sheets. Plaque-type psoriasis occurs in 80--90 percent of all cases and tends to persist for long periods. It affects mostly the elbows, knees, scalp, and lower back. It can, however, involve any part of the body.
The condition commonly appears in a symmetrical pattern (e.g., if the right elbow is affected, the left elbow might also be affected) and can also involve the scalp. When the scalp is affected, it can be intensely itchy. Scalp psoriasis can be one of the most frustrating and difficult areas to treat.
Plaque-type psoriasis can affect the genitals. Men are more likely to be affected in this location than women. Genital lesions can cause embarrassment during sexual relations, especially if the penis is affected. Affected areas of skin can become redder and more noticeable after intercourse. It is important that affected people are aware that lesions are not contagious, so they can reassure themselves and advise sexual partners.
Often patients are too embarrassed to tell their doctors that genital areas are affected. However, it is important to tell your doctor as there are treatments to help control psoriasis in these locations. Topical corticosteroids are usually effective in treating genital psoriasis. However, thinning of the skin (atrophy) and stretch marks (striae) can occur when potent steroids are applied for prolonged periods to such sensitive areas. In general, lower potency topical steroids are used in areas where the skin is thin. Higher potency topical steroids generally should be avoided on the genitals.
Newer, nonsteroidal treatments known as calcineurin inhibitors or topical immunomodulators (tacrolimus/protopic 0.1 percent and 0.3 percent and pimecrolimus/elidel 1 percent cream) have been used in psoriasis. Calcineurin inhibitors offer the advantage of being steroid-free, with no risk of stretch marks or thinning of the skin. Applying anthralin or coal tar products to genital lesions is not recommended as they can cause irritation.
The palms of the hands and soles of the feet can also be affected, although less frequently in plaque-type psoriasis. The lesions can be commonly noted on the pressure-bearing areas of the hands and feet.
Guttate Psoriasis
The Latin word gutta, meaning "droplet," describes the physical appearance of the lesions in this type of psoriasis. In guttate psoriasis, patients often describe the sudden appearance of small (1/8 inch/2-3 millimeters in diameter), raised, scaling bumps. Classically, guttate psoriasis can start in childhood or teenage years after streptococcal infections of the throat (streptococcal pharyngitis) or tonsillitis. A sudden flare-up of numerous tiny red, raised bumps (papules) covering large areas of the body can arise two to four weeks after the illness. The number of lesions can increase and spread rapidly over the trunk, arms, legs, and sometimes the face.
In children, an episode of guttate psoriasis usually clears up after the initial episode and does not recur. However, chronic psoriasis can follow. In adults, guttate psoriasis can develop into plaque-type psoriasis. Phototherapy is particularly effective for guttate psoriasis. To find out more, you can check out Types Of Psoriasis.