Risk of fungal infections in psoriasis patients receiving biologics

In recent years, biological agents have emerged as promising therapeutic options for managing psoriasis. The US FDA has approved around a dozen biologics to manage psoriasis, which include tumour necrosis factor (TNF)-α inhibitors, IL12/23 inhibitors, IL-17 inhibitors, and IL-23 inhibitors. While biologics have been established as a safe and efficacious treatment for managing psoriasis, there are concerns regarding their immunosuppressive effects that may place patients at an increased risk of various infections. TNF-α inhibitors like infliximab, etanercept, and adalimumab have been associated with an increased risk of opportunistic infections such as histoplasmosis, aspergillosis, and coccidioidomycosis, while IL-17 inhibitors predispose patients to mucocutaneous candidiasis. There are lacunae in our understanding of the types of these infections and the mechanisms causing increased susceptibility to various infections. This review offers a comprehensive summary of fungal infections reported in patients on biologics for psoriasis in various trials and real-life studies and attempts to summarise the mechanism, as demonstrated in various clinical trials and animal studies. An increased risk of invasive fungal infections has been seen in patients treated with TNF-α inhibitors as compared to IL-17 and IL-12/23 inhibitors. There is an increased risk of chronic mucocutaneous candidiasis in elderly patients with diabetes when treated with IL-17 inhibitors, however, most of these infections are mild to moderate in severity, rarely affecting the course of the therapy. Clinicians may benefit from being cautiously optimistic in prescribing biologics while maintaining a high index of suspicion for unusual pathogens, including invasive fungal infections.