Epidemiology
Psoriasis affects both sexes equally, and can occur at any age, although it most commonly appears for the first time between the ages of 15 and 25 years.
The prevalence of psoriasis in Western populations is estimated to be around 2-3%. The prevalence of psoriasis among 7.5 million patients who were registered with a general practitioner in the United Kingdom was 1.5%. A survey conducted by the National Psoriasis Foundation (a US-based psoriasis education and advocacy group) found a prevalence of 2.1% among adult Americans. The study found 35% of people with psoriasis could be classified as having moderate to severe psoriasis.
Around one-third of people with psoriasis report a family history of the disease, and researchers have identified genetic loci associated with the condition. Studies of monozygotic twins suggest a 70% chance of a twin developing psoriasis if the other twin has psoriasis. The concordance is around 20% for dizygotic twins. These findings suggest both a genetic predisposition and an environmental response in developing psoriasis.
Onset before age 40 usually indicates a greater genetic susceptibility and a more severe or recurrent course of psoriasis.
Read more about this topic: Psoriasis