Symptoms:

Psoriasis can appear suddenly or slowly. In many cases, psoriasis goes away and then flares up again repeatedly over time.

People with psoriasis have irritated patches of skin. The redness is most often seen on the elbows, knees, and trunk, but it can appear anywhere on the body. For example, there may be flaky patches on the scalp.

The skin patches or dots may be:

• Itchy
• Dry and covered with silver, flaky skin (scales)
• Pink-red in color (like the color of salmon)
• Raised and thick

Other symptoms may include:

• Genital lesions in males
• Joint pain or aching (psoriatic arthritis)
• Nail changes, including nail thickening, yellow-brown spots, dents (pits) on the nail surface, and separation of the nail from the base
• Severe dandruff on the scalp

Psoriasis may affect any or all parts of the skin. There are five main types of psoriasis:

• Erythrodermic -- The skin redness is very intense and covers a large area.
• Guttate -- Small, pink-red spots appear on the skin.
• Inverse -- Skin redness and irritation occurs in the armpits, groin, and in between overlapping skin.
• Plaque -- Thick, red patches of skin are covered by flaky, silver-white scales. This is the most common type of psoriasis.
• Pustular -- White blisters are surrounded by red, irritated skin.

Signs and tests:

Your doctor will look at your skin. Diagnosis is usually based on what the skin looks like.

Sometimes, a skin biopsy is done to rule out other possible conditions. If you have joint pain, your doctor may order x-rays.