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.
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.
