PLA2R1 and idiopathic membranous glomerulonephritis: Among cases of primary MGN with both PLA2R1 and THSD7A negativity, the frequency of NELL1-associated MGN was 6.7% (3/45) in France [6], 5.1% (2/39) in Belgium [29], 34.9% (15/43) in China [30].