The first step in diagnosing psoriasis is examining the affected area of skin. In some situations, a skin biopsy is required. Identifying the type of psoriasis a patient has is another important part of the process.
Psoriasis is a chronic skin disease that affects 2 percent to 2.6 percent of the United States population. This skin condition causes areas of thickened, swollen, and red skin, often covered with silver scales. A psoriasis diagnosis is usually made by examining the area of affected skin. Occasionally, doctors may find it difficult to diagnose psoriasis because it often looks like other skin diseases.
In some cases, it may be necessary to confirm a psoriasis diagnosis by examining a small skin sample under a microscope. This is called a skin biopsy.
In making a diagnosis, the doctor will also identify the psoriasis type.
There are several types of psoriasis. Some of these include:
- Plaque psoriasis. Skin lesions are red at the base and covered by silvery scales.
- Guttate psoriasis. Small, drop-shaped lesions appear on the trunk, limbs, and scalp. Guttate psoriasis is most often triggered by upper respiratory infections (for example, a sore throat caused by streptococcal bacteria).
- Pustular psoriasis. Blisters of noninfectious pus appear on the skin. Attacks of pustular psoriasis may be triggered by medications, infections, stress, or exposure to certain chemicals.
- Inverse psoriasis. Smooth, red patches occur in the folds of the skin near the genitals, under the breasts, or in the armpits. The psoriasis symptoms may be worsened by friction and sweating.
- Erythrodermic psoriasis. Widespread reddening and scaling of the skin may be a reaction to severe sunburn or to taking corticosteroids (cortisone) or other medications. It can also be caused by a prolonged period of increased activity of psoriasis that is poorly controlled.
- Psoriatic arthritis. Joint inflammation that produces symptoms of arthritis in patients who have or will develop psoriasis.