Patients with psoriasis generally have a higher risk of infection than those without psoriasis. This is not surprising, as they also have a higher risk of diabetes and metabolic syndrome, with obesity being a major risk factor for both psoriasis and infection. In addition, certain systemic therapies for psoriasis may add to the risk of infection, with some agents and classes more strongly implicated than others.

Interestingly, the relationship between infection and psoriasis may be bidirectional. For instance, specific infections, including streptococcal infection, may trigger psoriasis, but it is also true that having psoriasis is associated with more serious infections. There might be an effect from the psoriasis itself, as suggested in the recent paper by Yiu et al from the British Journal of Dermatology. This study attempted to control for confounders such as high body mass index and lifestyle behaviors such as smoking and alcohol consumption. The authors noted a small increased risk of serious infection in patients with psoriasis compared with those without psoriasis, noting that patients should not be unduly concerned about the risk of serious infection from psoriasis, since the absolute risks are small.

The treatments that we prescribe to our patients with psoriasis, depending on the drug, could also increase the risk of infections. TNF inhibitors such as infliximab can increase the risk of opportunistic fungal and bacterial infections, as well as tuberculosis. If a patient with psoriasis tests positive for latent tuberculosis, they need to receive appropriate treatment before starting a drug for their psoriasis, and a TNF inhibitor would not be my first choice in that setting.

With the newer therapies (ie, IL-17 and IL-23 blockers), tuberculosis does not appear to be as much of an issue. For instance, in our pooled cohort study of 12,319 patients with psoriasis, psoriatic arthritis, or ankylosing spondylitis, we found that secukinumab was not associated with an increased risk of active tuberculosis or tuberculosis reactivation in patients with a history of latent tuberculosis infection. Ustekinumab, which is an IL-12/IL-23 blocker, also has a lower risk of infection than the TNF blockers. The IL-17 and IL-23 inhibitors, along with apremilast, have a very low risk of serious infection and are very safe treatments for patients with psoriasis, and this is important information to reassure the patient.

Nonetheless, all of the systemic agents that we use in the treatment of psoriasis have at least some risks related to infection, and therefore the prescribing information includes warnings for increased risk of infection. Likewise, when clinically important chronic or acute infection does occur, it is recommended that consideration be given to temporarily discontinuing systemic therapy.