Psoriasis encompasses a group of related immune‐mediated inflammatory skin diseases that affect up to 3% of the population. These diseases are heritable and over 40 genetic susceptibility loci have been identified, many of which are involved in antigen presentation, cytokine signalling or innate antimicrobial responses. The commonest presentation of psoriasis is plaque psoriasis but the disease is clinically hetereogeneous in its manifestations and natural history depending on the age of the patient, environmental triggers and the sites affected. Distinct but related phenotypes include psoriatic arthritis, palmoplantar pustulosis and generalized pustular psoriasis. Psoriasis is associated with co‐morbidities including obesity, diabetes, vascular disease, depression and inflammatory bowel disease, which contribute to the considerable morbidity and increased mortality. Treatments include topical agents for disease of limited extent, phototherapy (UVB, PUVA) and systemic therapy (methotrexate, ciclosporin, acitretin, fumarates) for more extensive disease, and biological treatment (tumour necrosis factor α inhibitors, ustekinumab) for severe resistant psoriasis.

Keywords psoriasis, psoriatic arthritis, palmoplantar pustulosis, pustular psoriasis, co‐morbidity, treatment, methotrexate, ciclosporin, tumour necrosis factor inhibitor