MS4A1 and idiopathic membranous glomerulonephritis: Rituximab is a chimeric monoclonal antibody that selectively binds the CD20 receptor of B cells.12 It has been demonstrated to achieve partial or complete sustained remission of idiopathic membranous nephropathy.14,27 It has also been used with some success in lupus nephritis and immunoglobulin-associated MPGN.13,16,28 However, there are limited studies on the use of rituximab for non-lupus FHN specifically.