Abstract
BackgroundPodocytic infolding glomerulopathy (PIG) is a recently described condition causing rare pathological changes to the glomeruli, and has attracted considerable attention. PIG is characterized by specific changes to the thickened glomerular basement membrane (GBM), including microspheres, microtubular structures, and podocytic infolding. Only a small number of cases of PIG have been reported. The clinical features and pathogenesis of this condition are still unclear. To elucidate the characteristics of this glomerulopathy, it is necessary to accumulate information from reported cases. We present here the first reported case of PIG with multiple myeloma.Case presentationA 79-year-old Japanese man was admitted to his local hospital with proteinuria, hypergammaglobulinemia, hypoalbuminemia, and kidney dysfunction. Laboratory tests revealed monoclonal IgG(λ) M proteins in the serum and Bence-Jones proteins in the urine. Bone marrow aspiration showed monoclonal plasma cell proliferation, indicating a diagnosis of multiple myeloma. Renal biopsy was performed to determine the cause of the proteinuria and kidney dysfunction. Histological examination of the biopsy specimen showed glomeruli with an irregularly thickened GBM and bubble-like structures in the capillary walls. Immunofluorescence staining did not show glomerular deposition of immunoglobulins, light chains, or complement components. Congo red staining did not show amyloid deposition. Electron microscopy showed an irregularly thickened GBM with unusual structures in the glomerular capillary walls including podocytic infolding and microspheres, suggesting PIG. There were no electron-dense deposits in the GBM, while various findings indicating podocyte injury were detected.ConclusionWe present here the first reported case of PIG in a patient with multiple myeloma. The mechanisms underlying the development of PIG in multiple myeloma are unknown, but may be associated with podocyte injury.
Highlights
Podocytic infolding glomerulopathy (PIG) is a recently described condition causing rare pathological changes to the glomeruli, and has attracted considerable attention
We present here the first reported case of PIG in a patient with multiple myeloma
The mechanisms underlying the development of PIG in multiple myeloma are unknown, but may be associated with podocyte injury
Summary
Podocytic infolding glomerulopathy (PIG) was recently described by Joh et al [1] and has attracted considerable attention because of the characteristic pathological changes to the glomeruli. Case presentation A 79-year-old Japanese man presented with proteinuria, hypoalbuminemia, and increasing kidney dysfunction, and was admitted to his local hospital He had a 3-year history of hypertension, hyperlipidemia, and hyperuricemia with mild kidney dysfunction (serum creatinine level 1.1 mg/dL at age 76 years). He had been treated with an angiotensin II receptor blocker, statin, and allopurinol for 3 years. There were no electron-dense deposits in the GBM These pathological changes were similar to those of the glomerulopathy recently described by Joh et al [1], suggesting a diagnosis of PIG. His proteinuria and his general condition slowly improved, but he died suddenly from a severe acute pulmonary infection 2 months after the introduction of steroid therapy
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