Microbial Dysbiosis Drives Photodermatoses Pathogenesis, Revealing Novel Intervention Strategies

Photodermatoses are inflammatory skin conditions like polymorphic light eruption (PLE) and chronic actinic dermatitis (CAD), primarily triggered or worsened by ultraviolet radiation (UVR). These conditions, including photoaggravated dermatoses like lupus erythematosus and even actinic keratosis (AK) and cutaneous squamous cell carcinoma (cSCC) due to chronic UVR, significantly impair patient quality of life and psychological health. Current treatments often focus on symptomatic relief or UV avoidance, but a deeper understanding of underlying mechanisms is needed. Recent advances reveal the skin microbiome plays a crucial role in maintaining skin barrier stability and regulating immune responses, suggesting its dysbiosis could contribute to inflammation and disease.

This comprehensive review synthesizes current research on the relationship between microbial dysbiosis and various photodermatoses, including polymorphic light eruption (PLE), chronic actinic dermatitis (CAD), actinic prurigo, solar urticaria, lupus erythematosus, actinic keratosis (AK), and cutaneous squamous cell carcinoma (cSCC). The authors integrated findings from numerous studies to elucidate the formation and pathogenic mechanisms of dysbiosis in these conditions. The review also explored potential intervention strategies targeting the skin microbiome, drawing conclusions from existing literature rather than conducting new experimental work.

The review consolidates evidence demonstrating a consistent pattern of dysbiotic microbiome in several photodermatoses. Key findings include a significant decrease in overall microbiome diversity and a notable increase in colonization by pathogenic bacteria, particularly Staphylococcus aureus. This dysbiosis is implicated in promoting inflammation and contributing to the progression of these skin diseases. For instance, PLE affects approximately 18% of the population in Europe, underscoring the widespread impact. The burden on patients is substantial, with around one-third reporting a Dermatology Life Quality Index (DLQI) score greater than 10, indicating a "very large" impact on quality of life. Furthermore, anxiety and depression levels in affected individuals are approximately twice those in the general population.

The review highlights that dysbiosis, characterized by decreased diversity and increased Staphylococcus aureus colonization, is a consistent feature across multiple photodermatoses, directly contributing to inflammation and disease pathogenesis.

The integrated findings suggest that the altered microbial environment disrupts the skin barrier and dysregulates immune responses, creating a pro-inflammatory state exacerbated by UVR exposure.