An adolescent case of xeroderma pigmentosum variant confirmed by the onset of sun exposure‐related skin cancer during Crohn's disease treatment

Abstract

The patient was a 16-year-old boy who was diagnosed with Crohn's disease at 13 years of age, who was treated with mesalazine, azathioprine, and infliximab. Concurrently, the patient developed small freckle-like pigmented spots on sun-exposed areas, which gradually increased in number. At 14 and 16 years of age, a blue-gray macule and a nodule appeared on his face, respectively. A histopathological examination revealed that the macule had only postinflammatory pigmentation, while the nodule was basal cell carcinoma. The sensitivity to UV-killing by colony formation of the patient's cells was normal but was enhanced by caffeine treatment. In addition, a pathologic mutation in the POLH gene was identified and a diagnosis of xeroderma pigmentosum variant (XP-V) was established. XP-V is a cutaneous type of XP that is commonly diagnosed from middle age after the induction of skin cancer on sun-exposed areas. Our patient had a genetically sensitive background (XP-V), and we considered that immunosuppressive agents for Crohn's disease may have enhanced the photocarcinogenesis at a young age.This finding implies that we should be careful about a skin cancer production and that protection from UV may be essential when pediatric patients with a genetic background of UV sensitivity take immunosuppressive agents.