Excerpt from Psoriasis

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Background

Psoriasis is a common skin disease. Ocular signs occur in approximately 10% of patients, and they are more common in men than in women. Patients with ocular findings almost always have psoriatic skin disease; however, it is rare for the eye to become involved before the skin.

Pathophysiology

Psoriasis involves hyperproliferation of the keratinocytes in the epidermis. The cause of the loss of control of keratinocyte turnover is unknown. However, environmental, genetic, and immunologic factors appear to play a role. Psoriasis is associated with certain human leukocyte antigen (HLA) alleles, particularly human leukocyte antigen Cw6 (HLA-Cw6). In some families, psoriasis is an autosomal dominant trait.

Disease exacerbations can be triggered by trauma, stress, alcohol, medications, and infection (eg, staphylococcal, streptococcal, human immunodeficiency virus). The epidermis is infiltrated by a large number of activated T cells, which appear to be capable of inducing keratinocyte proliferation. Conjunctival impression cytology demonstrated a higher incidence of squamous metaplasia, neutrophil clumping, and nuclear chromatin changes in patients with psoriasis.

Frequency

United States

This condition affects 1-2% of the population. Approximately 6.4 million Americans have psoriasis.

International

Internationally, the incidence of psoriasis varies dramatically. A study of 26,000 South American Indians did not reveal a single case of psoriasis. In the Faeroe Islands, an incidence of 2.8% was observed.

Sex

Psoriasis appears to be slightly more prevalent among women than among men; however, men are thought to be more likely to experience the ocular disease.

Age

• Psoriasis can begin at any age. The median age of onset is 28 years.
• About 10-15% patients have onset of psoriasis before age 10 years.

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