The occurrence of a Kaposi sarcoma during the course of a therapy for a pemphigus vulgaris is reported. Only five such associations have been previously described in the literature. On the other hand, several works have reported simultaneous occurrence of a Kaposi sarcoma with anomalies of the immune or lymphoïd systems (lymphoma, Hodgkin disease, Waldenström disease, mycosis fongoïdes. Hypothesis concerning the Kaposi sarcoma genesis can be suggested on the basis of these observations and remain to be confirmed.