C3 and C3 glomerulonephritis: C3 glomerulonephritis (C3 GN) is a recently defined glomerulonephritis characterized by glomerular deposition composed of C3 with minimal or no immunoglobulin.[1,2] The disease is caused by abnormal activation of the alternative complement pathway and may be associated with several conditions that result in dysregulation of the pathway such as infection[3] and monoclonal gammopathy.[4] As a relatively newly recognized entity, data regarding the clinical and pathological features of C3 GN remain limited, and its association with other systemic/renal diseases is not well understood.