Background

Psoriasis is a chronic inflammatory skin disease that is characterized by thick, raised, bright red and pink plaques with a silvery scale.  The most common form is plaque psoriasis, which typically involves the scalp, elbows, knees, and back.  It is estimated to affect between 1% and 8.5% of adults worldwide and becomes more common with increased distance from the equator.  In the United Sates, it affects about 2% of the population.  Psoriasis is much less commonly seen in children.  The onset of psoriasis peaks in the fourth decade and again between the ages of 50 and 69.

Psoriasis is generally regarded as a disorder of the immune system that leads to the production of proinflammatory cytokines and overproduction and abnormal maturation of the outer layer of skin cells.  While genetics plays a big role in the development of psoriasis, behavioral and environmental factors clearly influence the course of the disease.  Infections, stress, trauma, and certain medications are known to initiate or worsen flares in people who have a genetic predisposition to developing psoriasis.  Additionally, smoking is clearly implicated in the onset and severity of psoriasis, with the incidence of psoriasis decreasing after successful smoking cessation.  Psoriasis has been linked with higher body mass index and increased alcohol intake as well.  Finally, some medications are known to worsen psoriasis.  These include lithium, beta-blockers, antimalarials, interferon, and rapid tapers of systemic corticosteroids.

Psoriasis is associated with several comorbidities including arthritis (psoriatic arthritis), cardiovascular disease, depression, diabetes, and metabolic syndrome, and nonmelanoma skin cancer.¹  It is important to screen for these and address them when present.