Progressive podocyte infolding glomerulopathy in a patient with systemic lupus erythematosus revealed by serial renal biopsies: a case report and literature review.

Podocyte infolding glomerulopathy (PIG) is a rare pathological diagnosis based on characteristic electron microscopic findings of microspheres and/or microtubular structures associated with podocyte infoldings into the glomerular basement membrane (GBM) and was proposed as a new entity from Japan in 2008. PIG has been increasingly reported not only in Japan but also worldwide; however, the precise cause and mechanisms of PIG are unknown. PIG cases investigated by repeated renal biopsies are even rarer. We herein report a patient with systemic lupus erythematosus (SLE) who showed progressive podocyte infoldings into GBM by serial renal biopsies and review previous reports of PIG comparing the findings of serial renal biopsies. PIG may progress in association with the activity of the underlying disease, particularly in patients with autoimmune diseases. In the present case, proteinuria persisted, and PIG progressed independently of the activity of SLE. Although PIG appears to follow a progressive course accompanied by proteinuria, further accumulation of data on PIG cases with serial renal biopsies will contribute to elucidating its pathophysiology.