Pathologic glomerular characteristics and glomerular basement membrane alterations in biopsy-proven thin basement membrane nephropathy
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Thin basement membrane nephropathy (TBMN) is diagnosed by diffuse thinning of the glomerular basement membrane (GBM) without any clinical and pathologic findings of Alport syndrome and the other renal diseases. TBMN is characterized clinically by benign familial hematuria but rarely develops into end-stage renal disease.
In 27 cases of biopsy-proven TBMN, we evaluated the pathologic characteristics of TBMN, and examined the correlation between these pathologic characterizations and renal dysfunction.
All patients had hematuria, and 21 patients (77.8%) had proteinuria. In six patients (28.6%) who were more than 50 years of age, the estimated glomerular filtration rate (eGFR) decreased from G3a to G4 in the chronic kidney disease stage. Pathologically, an irregular decrease in intensity of type IV collagen α5(IV) chain was seen in GBM, and irregular thinning with diffuse rough etched images was observed on the GBM surface with several sizes of holes by low-vacuum scanning electron microscopy. The glomerular morphology of TBMN was characterized by an increased number of small glomerular capillaries with an increased extracellular matrix (ECM). These characteristic morphologic alterations were evident from a young age in patients with TBMN, but were not correlated directly with the decrease of eGFR, the degree of hematuria, and proteinuria. The decrease of eGFR in patients with TBMN who were more than 50 years of age might be primarily mediated by arteriolosclerosis-associated glomerulosclerosis and interstitial fibrosis.
Characteristic pathological glomerular findings and GBM alterations occurred from a young age but were not associated directly with renal impairment in biopsy-proven TBMN.
KeywordsGlomerular basement membrane Low-vacuum scanning electron microscopy α5(IV) chain of type IV collagen Pathology Thin basement membrane nephropathy
We express special thanks to Shinya Nagasaka, PhD, Mr. Takashi Arai, Ms. Mitue Kataoka, Ms. Kyoko Wakamatsu, Ms. Arimi Ishikawa, and Ms. Naomi Kuwahara for the expert technical assistance.
This study was supported in part by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science; (C) no. 17K09717 (AS).
Compliance with ethical standards
Conflict of interest
The authors have declared that no conflict of interest exists.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee at which the studies were conducted (IRB approval number 30-06-948) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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