Membranous glomerulopephritis (aka membranous nephropathy, p 584 FA 2019) may occur secondary to drugs such as penicillamine. Immunofluorescence shows granular deposits due to immune complex deposition. Will also see diffuse capillary and GBM thickening, and SEM will show spike and dome appearance due to subepithelial deposits.
Membranous Glomerulonephritis is Nephrotic; ONLY PROTEINURIA is in the vignette
It can't be MPGN because MPGN is Nephritic with possible Nephrotic
Other choices are eliminated by Renal Biopsy
It sounds a lot like PSGN, but PSGN is nephritic and we would see pronounced hematuria with minimal proteinuria.