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E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
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Abstract titles should be brief and reflect the content of the abstract.
Podocytic infolding glomerulopathy (PIG) is a rare ultrastructural finding in renal biopsies, first described in Japanese case series. It is characterized by an invagination of the podocyte cell membrane (cytoplasmic projections) into the glomerular basement membrane. PIG is frequently associated with autoimmune conditions. It remains unclear whether it represents merely an accompanying feature of glomerular diseases or a distinct pathological entity.
We present a case series of patients from our hospital who were diagnosed with PIG on electron microscopy. Variables were analyzed to identify common histopathological and clinical features.
Since 2022, we have diagnosed three patients with PIG. All had membranous nephropathy (MN) as their main diagnosis and were positive for the anti-phospholipase A2 receptor (PLA2R).
All were Caucasian men, aged between 49 and 75 years. The initial presentation was nephrotic syndrome with proteinuria greater than 7 g/24 h. One patient presented with a relapse. Serum creatinine ranged from 1.1 to 1.5 mg/dL and hematuria was present in two patients. Antinuclear antibodies were negative in all of them.
High anti-PLA2R titers (>600 U/mL) were observed in two patients; the relapsing case showed intermediate levels but prior positivity at disease onset, suggesting persistent immunologic activity.
Light microscopy revealed normocellular glomeruli with mild mesangial matrix expansion with subepithelial spikes (fig 1). Immunofluorescence was positive for IgG (≥ ++/++++) with mild C3 deposition on glomerular basement membranes (fig 2). Ultrastructural study showed diffuse podocyte foot process effacement, subepithelial electron-dense deposits and uniformly-sized spherical particles with obscured membrane, measuring 50-75 nm in diameter (fig 3).
Immunosuppressive therapy was initiated in all cases. Two patients showed only a partial response to the first agent (one to cyclophosphamide and one to rituximab), prompting treatment to be switched. The third patient is currently under treatment with rituximab.
Our three patients had PIG associated with anti-PLA2R-positive primary MN. The observation that two patients showed only a partial response to initial therapy and one experienced a relapse suggests that PIG may represent more than just an ultrastructural feature, potentially influencing the prognosis and natural history of the main disease. Since the initial description by Joh et al. from Japan (2008), only a limited number of cases have been reported in the literature. The nature of PIG remains controversial, as it is uncertain whether it represents a distinct pathological entity or a morphological pattern associated with certain, mainly autoimmune, diseases. The cause of podocyte injury in this disease remains to be elucidated in the future.
