title: A case of podocytic infolding glomerulopathy with multiple myeloma.
abstract: BACKGROUND
  Podocytic 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.
  
  
  METHODS
  A 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.
  
  
  CONCLUSIONS
  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.
authors: Makoto
authors: M
authors: Harada
authors: Department of Nephrology, Shinshu University School of Medicine, 3-1-1, Asahi, Matsumoto, Nagano 390-8621, Japan. yujibeat@shinshu-u.ac.jp.
authors: Yuji
authors: Y
authors: Kamijo
authors: Takashi
authors: T
authors: Ehara
authors: Hisashi
authors: H
authors: Shimojo
authors: Hidekazu
authors: H
authors: Shigematsu
authors: Makoto
authors: M
authors: Higuchi
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D050533:Glomerular Basement Membrane / Q000473:pathology*; D015433:Glomerulonephritis, Membranous / Q000473:pathology*; D006801:Humans; D008297:Male; D009101:Multiple Myeloma / Q000150:complications* / Q000473:pathology*; D050199:Podocytes / Q000473:pathology*