CD40LG and idiopathic membranous glomerulonephritis: Although immunofluorescence examination can aid in differentiating LN-V from PMN given the absence of IgM, IgA, and C1q in the latter, it has been noted that these differences can be challenging due to the overlap that can occur.[20, 29] This may explain the presence, in a few PMN patients, of positive IgA, IgM and C1q despite these patients testing negative for all common secondary causes of MGN.