In one previous cohort [22], two cases initially diagnosed with weak primary membranous nephropathy and partial positivity for EXT1/EXT2 were negative for PLA2R on glomeruli in the first renal biopsy, but by around 6–10 years later, both cases had developed full-blown clinical lupus, and glomerular EXT1/EXT2 staining by IF was strongly positive on the second or third biopsy. Here, EXT1 is linked to systemic lupus erythematosus.