Anti-glomerular basement membrane (GBM) antibody nephritis is defined by linear immunofluorescence staining of GBM by immunoglobulin G (IgG), typically associated with GBM rupture, fibrinoid necrosis, and crescent formation. Clinically, the patients present with rapidly worsening renal function, often with hematuria. Typical renal pathologic findings include necrotizing and crescentic glomerulonephritis. In contrast, thrombotic microangiopathy (TMA) is characterized by microvascular thrombosis, which can also lead to acute kidney injury. Thrombotic microangiopathy is associated with some systemic diseases and has characteristic clinical features of microangiopathic hemolytic anemia, platelet consumption, and multiple organ failure. Anti-GBM nephritis associated with TMA has rarely been reported. We describe an unusual case of atypical anti-GBM disease without crescent formation or necrosis but with light microscopic and ultrastructural features consistent with endothelial cell injury and glomerular-limited TMA.

The sequential or simultaneous presentation of anti-glomerular basement membrane (anti-GBM) glomerulonephritis with membranous nephropathy (MN) has been infrequently reported. Although the mechanism underlying MN superimposed on anti-GBM glomerulonephritis is unknown, the two entities are believed to be interrelated. We report the case of a 75-year-old woman diagnosed with rapidly progressive glomerulonephritis. Renal biopsy revealed crescentic glomerulonephritis with linear and granular staining of immunofluorescent IgG1 and IgG4 granular staining on the capillary loops. Electron microscopy revealed extensive subepithelial deposits. These findings suggested simultaneous development of anti-GBM glomerulonephritis and MN in this case. Serum phospholipase A2 receptor (PLA2R) antibody was negative. The patient was treated with prednisolone and plasma exchange, resulting in resolution of renal insufficiency and a decrease in urinary protein. The rapid decrease in urinary protein and absence of PLA2R antibody suggest that the mechanism of MN associated with anti-GBM glomerulonephritis differs from that of primary MN.

A 46-year-old Japanese male with a past medical history of microscopic hematuria presented with nausea, vomiting, and abdominal pain for which he had been diagnosed with rapidly progressive glomerulonephritis with a peak serum creatinine of 6.6 mg/dL and anti-glomerular basement membrane antibody of 214 EU. Light microscopy showed cellular crescent formation, and immunofluorescence illustrated both linear staining of IgG along the glomerular basement membrane and granular staining of IgA and C3 in the mesangial area; however, the PAS staining of mesangial expansions and mesangial proliferations were not observed. Clinical and histological findings suggested anti-glomerular basement membrane glomerulonephritis with mesangial IgA deposition, suggesting IgA nephropathy, a rare condition.