Some or all of the fingernails and toenails are affected in about 50 per cent of patients, and a proportion of patients also suffer from psoriatic arthritis. In addition, psoriasis is associated with blood lipid abnormalities, obesity, diabetes and cardiovascular diseases (e.g. myocardial infarction, hypertension). Patients also often experience low self-esteem, depression, social isolation and stigmatisation.

The Dermatology Life Quality Index (DLQI) is a validated quality of life measure for people with skin diseases that is incorporated into National Institute for Health and Care Excellence (NICE) Technology Appraisals for the use of biologics in psoriasis. It is based on 10 questions that explore aspects of the disease that are important to patients, such as discomfort caused by the disease and whether the disease has interfered with work or study. It gives a score between 0 and 30 €“ above 10 is interpreted as having a large impact on quality of life.