Medical Dermatology - Psoriasis

Psoriasis affects approximately two percent of the U.S. population and 150,000 new cases are diagnosed each year. Psoriasis  is a chronic skin condition that can occur over a large percentage of the body but is usually found on very characteristic sites such as the elbows, knees, nails and scalp. Although psoriasis is very common in some families, it is not a contagious disease; it cannot be passed from one person to another. The skin lesions are generally described as red (erythematous) plaques with thick white scale.

With a classic presentation the diagnosis of psoriasis is seldom missed. However, some patients have non-classic presentations, and they may go undiagnosed for years before being seen by a dermatologist. Even to the trained dermatologist, a skin biopsy is sometimes needed to confirm the diagnosis. Once psoriasis is diagnosed, therapy may be as simple as a topical steroid cream once or twice a day. Other times more advanced treatment is required. Therapy is often customized to the individual patient. With a growing number of treatment options, patients with moderate to severe psoriasis may benefit from seeking  care from a board-certified dermatologist.

What causes psoriasis?

Although the cause of psoriasis is still debated, psoriasis is likely a result of an abnormal immune response. Skin biopsies show a characteristic pattern of infiltration of white blood cells. This, in turn, causes abnormal skin growth. Specifically, the skin at psoriasis sites grows too rapidly, resulting in a scaly appearance. The skin also changes in other ways. For example, blood vessels approach the surface of the skin resulting in easy bleeding when scales are picked or knocked off. Individuals with psoriasis often have a genetic predisposition for the disease, which is why it can run in families. 

Types of Psoriasis 

• Classical lesions occur on the scalp, elbow, knees, legs, arms, genitals, nails, palms, and soles.
• Inverse psoriasis occurs in skin folds and has little scale if any. It looks very different than classic psoriasis lesions.
• Guttate psoriasis affects children and young adults and appears as numerous small lesions scattered over the body.
• Pustular psoriasis has, in addition to characteristic psoriatic lesions, pustules with thick purulent material (pus) and is often found on the palm of the hands.
• Psoriatic arthritis is found in 30 percent of individuals with psoriasis. It does not respond to topical therapy.