EXT1 and Autoimmunity: The antigens in secondary MN remained unknown until Sethi et al detected EXT1/EXT2 in both pure class V LN (8/18 patients) and in presumed primary MN associated with signs of autoimmunity (3/16 patients).[4] These findings suggest that EXT1/EXT2 may represent the common target antigen of secondary (autoimmune) MN and could identify this special subset of LN.