Fig 3. Immunofluorescence shows mesangial or even paramesangial staining for C1q in C1q nephropathy, typically with lesser intensity staining for immunoglobulin (Ig) and C3. The immunofluorescence findings in C1q nephropathy are crucial in making the diagnosis and ruling out possible IgA nephropathy. In this glomerulus, sharply defined mesangial C1q was present, corresponding to electron-dense immune complex-type deposits seen by electron microscopy (see Fig 4). (Immunofluorescence with anti-C1q, X200).