Obesity and its role in the management of rheumatoid and psoriatic arthritis.

In the last decade, interest has been growing in the relationship between obesity and several other clinical conditions, besides the well-established links between body mass index (BMI) and cardiovascular diseases or cancer. A particular focus has been put on the impact of a higher BMI on immune-mediated diseases such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Obesity has been found to be associated with greater arthritis activity and a reduced probability of response to anti-tumor necrosis factor (TNF) agents. On the other hand, weight loss increases the chances of treatment success. Although the direct effect of a higher body mass on drug clearance might in part account for this obesity-related effect, other biological mechanisms could be involved. The evidence of a negative influence of obesity on arthritis treatment is particularly strong as far as anti-TNF inhibition is concerned; on the contrary, the response to biologic agents targeting interleukin-6, cytotoxic T lymphocyte antigen 4, or CD20 seems not to be negatively affected by a higher BMI. In this review, we will consider the main studies investigating the influence of obesity on anti-rheumatic treatment in RA and PsA patients. We will also try to hypothesize about a possible pathogenic explanation of this phenomenon and its role in the choice of an appropriate and personalized therapy.