Skin cancers in patients of skin phototype V or VI with xeroderma pigmentosum type C (XP-C): A retrospective study

Xeroderma pigmentosum (XP) is a rare genetic disease comprising 7 subgroups, A to G, all of which are associated with early onset of several forms of skin cancer. Our main objective was to determine the prevalence of skin cancers in a cohort of dark-skinned XP-C patients in Mayotte.A single-centre cohort consisting of all XP patients was followed in the island of Mayotte from December 2015 to May 2017 by dermatologists from the University Hospital of Saint-Denis (Reunion) during the course of dermatological missions.Eighteen patients of median age 12.9 years (7 female/11 male) belonging to 14 families were included. All had XP-C and carried the same mutation. Median age at clinical diagnosis of XP was 1.8 years. A total of 144 skin cancers (94 squamous cell carcinomas [SCC], 30 basal cell carcinomas [BCC], 14 melanomas, 5 sarcomas and 1 sarcomatoid carcinoma) were observed in 11 of the 18 patients (61%). Eleven patients (61%) had at least 1 SCC, 6 (33%) had at least 1 BCC, 6 (33%) had at least 1 melanoma, and 4 (22%) had at least 1 sarcoma. In all, 95.5% of the cancers occurred in light-exposed skin areas. Median age was 5.4 years for the initial cancer and 6.4 years for the second. SCCs and sarcomas occurred earlier than CBCs and melanomas (P0.0001). All patients had mild to severe poikiloderma and presented photophobia, and 50% had pigmented palmoplantar lesions. One-third had oral mucosal involvement while 78% had ocular or palpebral lesions. Nail and hair involvement was recorded in 17% of patients. The median sun protection score (evaluated on a 7-item scale) was 6/7. The median score on the quality-of-life questionnaire (DLQI) was 4/30. Severity of poikiloderma was significantly correlated with the occurrence of skin cancers.Our cohort showed a high prevalence of skin cancer in XP-C patients of phototype V and VI exposed to UV radiation in a tropical region. SCCs were the most common tumours. The prevalence of melanoma was high, with major risk compared to controls of the same skin phototype. In addition, we found a high prevalence of sarcomas (5 patients). Initial cancers occurred early (5.4 years) compared to data from the literature, and SCCs and sarcomas occurred significantly sooner than melanomas and BCCs.