Psoriasis: The Basics

Psoriasis is a chronic, non-cureable skin condition. It has an overall prevalence of 1 to 5% of the general population. That means for every one hundred people, there are up to 5 people with psoriasis, worldwide. Psoriasis is seen more frequently in some families, suggesting a genetic role. Recent research in fact, suggests multiple genes predispose an individual to this condition (polygenic inheritance). Various environmental triggers, such as trauma, infections or medications may induce psoriasis in a predisposed individual. Stress is a well-known trigger and often patients note a flare of their psoriasis during periods of stress. Psoriasis may first appear at any age. However, there are two main peaks of age of onset, between the ages of 20 to 30 and at 50 to 60 years. Streptococcal infections may provoke or aggravate psoriasis. Several medications such as lithium, beta-blockers, antimalarials and interferon can induce psoriasis in the predisposed individual.

The clinical features of psoriasis involve, sharply demarcated, reddish, scaly lesions, classically involving the elbows and knees and scalp. Psoriasis may involve any part of the skin, including the palms, soles and genital area. Nail involvement may occur, often distorting the appearance of the nail, leaving pits or a whitish, crumbly or poorly adherent nail resembling a fungal infection. I sometimes see patients with psoriasis who have been treated by a non-specialist with oral antifungals for presumed nail infection, when in fact, they just had psoriasis of the nails. Of note, psoriasis can be accompanied by arthritis in about 5 to 25% of the patients with psoriasis.

A large body of literature has shown that psoriasis is associated with a variety of other conditions characterized by chronic inflammation, including, hypertension (high blood pressure), myocardial infarction (heart attack), stroke, obesity and diabetes mellitus.

There are a variety of topically applied treatments for psoriasis, which include, topical corticosteroid creams and ointments, vitamin D3 analogs (vectical and calcipotriol) and topical retinoids.

Systemic treatments for psoriasis include oral medications, such as, methotrexate, which is considered first-line systemic therapy for psoriasis. Methotrexate inhibits DNA synthesis, thus slowing the proliferation rate of the psoriatic immune cells. Methotrexate is prescribed for patients with moderate to severe psoriasis and it does require blood testing for monitoring of the blood count and liver enzymes. Biologic drugs, sometimes referred to as “biologics” are a newer class of drugs that block a molecule that stimulates the immune system (TNF-alpha). Drugs of this category include Enbrel, Humira, and Remicade. Perhaps the oldest treatment for psoriasis has been sunlight. It is well-known that UV radiation from sunlight induces suppression of the immune cells in the skin. Light therapy, so-called narrow-band UVB treatment is considered in patients with more generalized lesions.