In the present study, we report the clinical characteristics of a unique systemic lupus erythematosus (SLE) multiplex family with 6 of its members affected by the disease, 1 of them being male. Four patients showed nephropathy, 2 of them with late-onset SLE (52 and 55-year-old), one with cutaneous and articular involvement, and another one developing lupus after 5 years undergoing highly active antiretroviral therapy (HAART) due to acquired immunodeficiency syndrome. Notwithstanding the genetic load, the fact that 2 patients showed late-onset disease, and the extreme delay of the appearance of SLE after HAART in the proband suggest that not only genetic, but other--mainly environmental--factors are necessarily required for the development of SLE.