Renal involvement in systemic lupus erythematosus (SLE) is a typical manifestation of the disease. The occurrence of non-lupus nephritis, especially IgA nephropathy (IgAN), in patients with SLE has rarely been reported. We describe the case of a 21-year-old woman who was diagnosed with IgAN and subacute necrotizing lymphadenitis, and her renal lesion biopsy was typical of lupus nephritis (ISN/RPS Class III). Although IgAN and lupus nephritis share some common physiopathological characteristics, their laboratory, histopathologic findings, and the extra-renal clinical manifestations are different and support a different pathogenesis. Our case highlights the importance of a renal biopsy in patients with lupus and urinary alterations despite underlying IgAN. A correct diagnosis would permit the most appropriate immunosuppressive treatments to be considered.

Keywords: Systemic lupus erythematosus, Lupus nephritis, IgA nephropathy, Subacute necrotizing lymphadenitis