Individuals with complete filaggrin deficiency may have an increased risk of squamous cell carcinoma

Funding sources: This work was supported by grants from the Aage Bangs Foundation, Aase Ejnar Danielsens Foundation and The Capital Region of Denmark, Foundation for Health Research. Conflicts of interest: none declared. Dear Editor, Loss‐of‐function mutations in the filaggrin gene (FLG) are observed in approximately 10% of Northern Europeans. Heterozygous and homozygous mutation carriers have, respectively, partial or complete reduction of epidermal filaggrin and its degradation products. Filaggrin is degraded to, among other things, transurocanic acid (trans‐UCA),1 a chromophore that provides protection against ultraviolet radiation (UVR) and modulates cutaneous immune functions.1 Accordingly, a deficiency of filaggrin leads to altered endogenous protection against UV exposure.1 Mutations in FLG are associated with atopic dermatitis (AD).2 Interestingly, individuals with AD appear to have an increased risk of developing nonmelanoma skin cancer, including squamous cell carcinoma (SCC).3 As SCC is strongly related to chronic ultraviolet (UV) exposure, we evaluated whether the prevalence of FLG mutations in patients diagnosed with SCC was higher than in controls from the general population. Briefly, 528 formalin‐fixed, consecutive, archived, anonymized, paraffin‐embedded blocks from patients diagnosed with SCC were retrieved from the Department of Pathology, Herlev Hospital, Copenhagen, Denmark. Approval was obtained from the local ethics committee (approval H‐4‐2011‐145).