C3G is defined by the predominant deposition of complement components, and C3 deposition is believed to play a causal role in the disease.5 As such, for drugs designed to inhibit C3 activation, reduction in C3c staining in the kidney tissue would provide confirmation of drug activity in patients with C3G in whom C3 deposition is not expected to spontaneously decrease/resolve. The gene discussed is C3; the disease is complement 3 glomerulopathy.