Psoriasis - Causes

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It seems reasonable to assume that pustular psoriasis, which resembles an infection, is caused by some organism, but none to date have been identified.

Skin Injuries and the Köbner Response. The Köbner response is a delayed response to skin injuries, in which psoriasis develops later on at the site of the injury. In some cases, even mild abrasions can cause an eruption, which may be a factor in the frequency of psoriasis on the elbows or knees. It should be noted that psoriasis can develop in areas with no history of skin injury.

Drugs. Numerous drugs can worsen or cause an eruption of pre-existing, inactive psoriasis, including the following:

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• The anti-malarial drug chloroquine
• Certain drugs used for hypertension and heart problems, including angiotensin-converting enzyme (ACE) inhibitors. Beta-blockers may actually trigger the onset of psoriasis and produce flare-ups in people who already have it.
• Progesterone used in female hormone therapies
• Lithium, which is used in bipolar disorder, may trigger the onset of the disease and cause severe flare-ups in people who already have psoriasis.
• Indomethacin, a non-steroidal anti-inflammatory drug (NSAID), can cause or worsen psoriasis. Other NSAIDs, such as meclofenamate, may actually improve the condition.
• Withdrawing from oral steroids (steroids taken by mouth), or from very strong steroid ointments that cover wide skin areas, can cause flare-ups of severe psoriasis. The flare-ups may be of various psoriatic forms, including guttate, pustular, and erythrodermic psoriasis. Because these drugs are also used to treat psoriasis, this rebound effect is of particular concern.
• Medications that cause rashes, a side effect of many drugs, can trigger psoriasis as part of the Köbner response.

Review Date: 10/30/2006
Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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