Subepithelial deposits with microspherular structures in membranous glomerulonephritis.

Rare cases of membranous glomerulopathy (MGN) with subepithelial deposits consisting of microspherular structures identified by electron microscopy have been described in the literature as either MGN with spherules or podocyte infolding glomerulopathy (PIG). The paucity of available studies shows a strong association with underlying autoimmune disease. To further understand the significance of subepithelial microspherular deposits, we retrospectively identified native kidney biopsies from 10 patients diagnosed as MGN with subepithelial microspherular structures identified by ultrastructural examination at the University of Rochester Medical Center (URMC) during an 11-year period. The majority were Caucasian (80%) with a mean age of 51.3 (±12.9) years. 50% had an autoimmune disorder, of which 80% were SLE. Two SLE cases had concomitant rheumatoid arthritis and Sjogren's syndrome. One additional case had antiphospholipid syndrome and showed lupus-like features on biopsy. 40% were idiopathic and negative for PLA2R, NELL1, and THSD7A. MGN with subepithelial microspherular structures is frequently associated with an underlying autoimmune disease. The majority are negative for markers of primary MGN (PLA2R, THSD7A, and NELL1) and show features suggestive of secondary MGN.