icd 9 code: Chronic Plaque Psoriasis
Chronic plaque psoriasis, the most common form of psoriasis, is a papulosquamous disease defined by erythematous plaques with a silvery scale. The diagnosis usually is clinical, but occasionally a biopsy is necessary. Psoriasis affects 0.6 to 4.8 percent of the U.S. population, and about 30 percent of affected patients have a first-degree relative with the disease. Psoriasis is a T-cell–mediated autoimmune disease, but certain medications and infections are well-known risk factors. Management of psoriasis includes education about chronicity, realistic expectations, and use of medication. Steroids and vitamin D derivatives (e.g., calcipotriene) are the mainstays of topical therapy. Topical steroids and calcipotriene together may work better than either agent alone. Patients with psoriasis involving more than 20 percent of their skin or those not responding to topical therapy are candidates for light therapy; traditional systemic therapy; or systemic treatment with immunomodulatory drugs such as alefacept, efalizumab, and etanercept.
The prevalence of psoriasis in the United States is estimated to be 0.6 to 4.8 percent. Psoriasis is slightly more common in men. No reliable data exist to support the common assumption that psoriasis is less common in blacks. There is a bimodal onset (i.e., late teens and late 50s), and early-onset disease is more common.
About 30 percent of patients with psoriasis have a first-degree relative with the disease, and those with early-onset disease are more likely to have a family history of psoriasis.These facts lend support for a genetic basis for the disease, and several chromosome loci have been implicated.The disease is not exclusively genetic, however, because several environmental factors also appear to play a roles.
Psoriasis is a T-cell–mediated autoimmune disorder.The process begins with an environmental factor, perhaps a viral antigen, which induces T cells to produce cytokines. The cytokines stimulate keratinocyte proliferation and production of antigenic adhesion molecules in the dermal blood vessels. These adhesion molecules further stimulate T cells to produce cytokines, thus perpetuating the response. Immunomodulatory drugs, which target the mechanism just described, offer novel treatment options for psoriasis. These drugs, also known as biologics, are discussed later.
Psoriasis is associated with several risk factors that may provide the environmental stimulus to T-cell proliferation. They include psychological stress, certain medications (lithium, beta blockers, antimalarial drugs, nonsteroidal anti-inflammatory drugs, and oral steroid withdrawal), and infection. Although a link between psoriasis and stress seems to exist, evidence to support a causal relationship is lacking. Chronic human immunodeficiency virus infection is associated with severe psoriasis exacerbations.
The diagnosis of psoriasis is based on the clinical appearance of skin lesions. Biopsy may be necessary, however, to distinguish psoriasis from other conditions with similar appearances such as lichen simplex chronicus, nummular eczema, seborrheic dermatitis, and tinea corporis.