[A whole family affected by xeroderma pigmentosum: clinical and genetic particularities]

Xeroderma pigmentosum is a relatively frequent genodermatosis in North Africa. It is characterized by abnormal sensitivity to ultraviolet light, responsible for the early occurrence of multiple cutaneous neoplasms. We present the results of the clinical and biological investigations in a family in which all its members exhibited xeroderma pigmentosum.

Since 1962, the father, mother, the 5 children and the maternal uncle were all followed-up in the dermatology department in Tunis for a variant of xeroderma pigmentosum. Clinical (dermatological, neurological and ophthalmologic), biological, photobiological and molecular biology investigations were carried out.

Diagnosis of a variant of xeroderma pigmentosum was established on the delayed appearance (after the age of 4) of poikiloderma and the early onset of multiple carcinomas, without neurological disorders. Fifty-eight squamous cell and 3 basal cell carcinomas were diagnosed and treated by surgical exeresis or radiotherapy. The third child, treated with etretinate for 6 years, had developed 38 carcinomas. Contrary to the parents, whose first carcinomas had appeared at the age of 34 and 40 years, the cutaneous cancers in the children appeared early, between the ages of 17 and 24. The minimal erythematous dose was normal in all these patients. Conversely, the phototest revealed persistent erythema and the delayed appearance of multiple dyskeratosis cells. Molecular biology confirmed the diagnosis of xeroderma pigmentosum with the presence of a low level DNA repair. The third child, the father and the uncle respectively exhibited DNA repair rates of 32, 57 and 72%, compared with normal controls. The results of the complementarity tests conducted in the third child suggested that this family belonged to the genetic F group. Discussion The clinical and molecular data confirmed the diagnosis of xeroderma pigmentosum in this family and their genetic F group profile. However, this family exhibited clinical (the cutaneous involvement was more severe in the children) and molecular heterogeneity and the level of DNA repair was high in comparison with the levels (between 12 and 15%) reported by Japanese authors in group F xeroderma pigmentosum. The third child exhibited 10-fold more carcinomas that his siblings. This high rate of carcinoma may be explained by excessive exposure to sun and/or the retinoid treatment, particularly since his DNA repair rate (32%) was relatively high compared with that of severe (0-5%) and moderate (5-15%) forms of the disease.