Incidence and Cancer Morbidity of Xeroderma Pigmentosum: A Swedish Population‐Based Register Study

Xeroderma pigmentosum (XP) is a rare autosomal recessive condition associated with an extreme sensitivity to ultraviolet radiation. The XP incidence and cancer risk have been estimated in clinical cohorts but no population-based analyses are available. We used the Swedish National Patient Register and the Swedish Cancer Register to estimate the incidence of XP and the standardized incidence ratios (SIRs) for cancers over 2001-2019. A total of 24 individuals with an XP diagnosis of Q82.1 met the inclusion criteria for the study, corresponding to an estimated birth incidence of 0.72/100,000 (1/138,984). Thirty-one cancers other than basal cell carcinomas (BCCs) were observed in six patients (SIR 20.5, 95% CI: 14.0-29.1). The SIR in males was higher compared to females (p = 0.001). The cumulative risk for melanoma or cutaneous squamous cell carcinoma (cSCC) was 69% by the age of 80. BCC was observed in all individuals with follow-up beyond the age of 50. While a noteworthy risk increase of cancer in individuals with XP was confirmed, the cancer incidences for melanoma, cSCC and BCC were lower compared to previous reports. The penetrance for melanoma and cSCC was incomplete at the age of 80 pointing to the possible effects of successful sun protection.