Direct immunofluorescence shows mesangial and capillary loop granular fluorescence.
Cases of idiopathic membranoproliferative glomerulonephritis usually show positivity for IgG and C3. Membranoproliferative glomerulonephritis, type I is a morphologic diagnosis, not an etiologic diagnosis. Cases of lupus glomerulonephritis and cryoglobulinemic glomerulonephritis frequently show a membranoproliferative, type I pattern of injury. I is more a morphologic pattern of injury that a single disease. Many cases are idiopathic.