Psoriasis - Diagnosis

Diagnosis

A microscopic examination of tissue taken from the affected skin patch is needed to make a definitive diagnosis of psoriasis and to distinguish it from other skin disorders. Usually in psoriasis, the examination will show a large number of dry skin cells, but without many signs of inflammation or infection. Specific changes in the nails are often strong signs of psoriasis.

Disease Severity

The severity of psoriasis ranges from one or two flaky inflamed patches to widespread pustular psoriasis that, in rare cases, can be life threatening. To help determine the best treatment for a patient, doctors usually classify the disease as mild to severe. The classification depends on how much of the skin is affected:

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• Mild psoriasis affects less than 3% of the body surface. Most cases of psoriasis are limited to less than 2% of the skin.
• Moderate psoriasis covers 3 - 10% of the skin.
• If more than 10% of the body is affected, the disease is considered severe.

The palm of the hand equals 1% of the body.

The severity of the disease is also measured by its effect on a person's quality of life.

The National Psoriasis Foundation has proposed a new classification method. The group suggests a two-tiered system that classifies patients as needing either local or body-wide (systemic) treatment.

In general, severe or widespread psoriasis is harder to treat. However, some forms of psoriasis can be very resistant to treatment, even though they are not categorized as severe. They include:

• Any psoriasis on the palms and soles (hand and foot psoriasis)
• Inverse psoriasis (which occurs in the folds of the skin)
• Scalp psoriasis
• Psoriatic arthritis

Review Date: 10/21/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).