[Staphylococcus-associated glomerulonephritis without IgA deposits: a case report].

Staphylococcus-associated glomerulonephritis (SAGN) represents a possible version of parainfectious glomerulonephritis and is a pathological entity that's now constantly increasing in developed countries. It is known how bacterial infections can be a possible trigger for various type of glomerulonephritis with clinical onset and evolution comparable to the ones observed in parainfectious glomerulonephritis. Furthermore, in clinical practice the identification and isolation of the pathogenic microorganism responsible for the development of parainfectious glomerulonephritis is not always possible. Therefore, in those cases in which SAGN is suspected, it is often necessary to recur to kidney biopsy in order to come to as much as possible correct diagnosis. Historically, according to scientific literature, the most distinctive anatomopathological feature of SAGN is represented by predominant or codominant mesangial IgA deposits, sometimes associated with C3 deposits. These findings make the differential diagnosis between SAGN and IgA nephropathy often necessary. However, many reports describe how SAGN can also be characterized by a varying spectrum of immunological deposits. In some cases, for example, IgA deposits can be absent and in some other cases it is described a net dominance of C3 deposits. In this case, it becomes extremely important to exclude a possible occurrence of C3 glomerulopathy (C3GN), considering how different are the therapeutic approach and the prognostic implications associated to it. However, the differential diagnosis between SAGN and C3GN can be very hard. Here's a case report about a patient who has been hospitalized into our Unit after developing a form of Staphylococcus Aureus associated glomerulonephritis which presented atypical anatomopathological features.