Pyoderma gangrenosum: pathogenetic mechanisms and their implications for treatment

Pyoderma gangrenosum (PG) is a rare inflammatory skin disease belonging to the group of neutrophilic dermatoses. The pathogenesis of PG involves a predisposing genetic background that facilitates a dysregulated innate and adaptive immune response, with an imbalance between pro-inflammatory and anti-inflammatory mediators, leading to neutrophil-driven inflammatory damage. Several immunosuppressants and immunomodulatory drugs are currently available for the treatment of PG, in combination with topical therapies, wound management and pain control strategies. Systemic corticosteroids and cyclosporine remain the first-line treatment options with the best evidence. However, in recent years, the rise of knowledge about different pathogenic mechanisms has led to a significant increase in studies attesting the efficacy and safety of biologic therapies including, among others, antagonists of tumour necrosis factor (TNF)-α and interleukin (IL)-23, becoming the drug of choice in specific clinical setting. Similarly, different small molecules such as JAK-STAT (Janus kinase/signal transducer and activator of transcription) inhibitors are showing promising results for the treatment of PG. We review established and emerging pathogenesis-driven treatments, also providing a therapeutic algorithm and informing future directions in the management of PG.