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

Background: 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.

Patients and methods: 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.

Results: 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 (P<0.0001). 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.

Discussion and conclusion: 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.