The relationship between smoking, psoriasis and psoriatic arthritis.

: Smoking is the single most important cause of preventable mortality worldwide. Besides being associated with major cardiovascular and bronchopulmonary diseases, and several cancers, it has been linked with a number of immune-related conditions, including psoriasis and psoriatic arthritis (PsA) We aimed to summarize data on the role of smoking in the development and prognosis of psoriasis and PsA, pointing to the consequences in terms of disease management. : Mechanisms, clinical manifestations, and comorbidities associated with smoking in psoriasis and PsA were reviewed by searching Medline, Embase and Cochrane Library databases for papers published between January 2000 and July 2018 using combination of terms. Articles not written in English were excluded. : Smoking is a risk factor for psoriasis development. As for PsA, smoking is positively associated with the disease at the population level, but it is negatively associated in patients with psoriasis. This phenomenon is referred to as the 'smoking paradox' of PsA. Smoking may cause poor response and reduced adherence to treatment of both psorasis and PsA. Physicians need to be aware of the smoking habits of their patients with psoriasis and PsA; whenever possible, smoking cessation programs should be considered.