Psoriasis is a genetically programmed inflammatory disease that affects primarily the skin in about 3% of individuals. Psoriasis begins as a small scaling papule. When multiple papules coalesce, they form scaling plaques.
These plaques tend to occur in the scalp, elbows, and knees. Although psoriatic plaques can be limited to only a few small areas, the condition can involve widespread areas of skin anywhere on the body.
These plaques can be itchy, and when the scale is peeled away, small bleeding points may appear. Psoriasis tends to occur in areas of trauma. This condition often waxes and wanes spontaneously.
Many patients with psoriasis have abnormal nails. Psoriatic nails often have a horizontal white or yellow margin at the tip of the nail called distal onycholysis because the nail is lifted away from the skin. There can often be small pits in the nail plate, and the nail is often yellow and crumbly.
Psoriasis can be associated with a destructive arthritis called psoriatic arthritis.
What causes Psoriasis?
It is now clear that there is a genetic basis for psoriasis. This hereditary predisposition is necessary before the disease can be triggered by environmental factors.
Psoriasis is often diagnosed by a competent physician or at least suspected on the basis of its appearance and distribution. Occasionally it may be necessary to remove a small piece of skin (a biopsy) and have it examined by a pathologist to confirm this conviction.
Topical treatments are very useful because they are relatively safe, quite effective, and can be applied directly to the disease. They take the form of lotions, foams, creams, ointments, gels, and shampoos. They include topical steroids, tar preparations, and calcium- modulating drugs.
For a more extensive disease, a useful option is ultraviolet light exposure.
There are lasers that produce UVL in wavelengths similar to narrow-band UVB can be quite effective for small plaques of psoriasis.
There are a variety of drugs administered systemically that are useful in controlling psoriasis. Drugs like methotrexate and cyclosporine are administered orally and can affect the liver, kidney, and bone marrow.