[HTML][HTML] Tubular proteinuria defined by a study of Dent's (CLCN5 mutation) and other tubular diseases

AGW Norden, SJ Scheinman… - Kidney international, 2000 - Elsevier
AGW Norden, SJ Scheinman, MM Deschodt-Lanckman, M Lapsley, JL Nortier, RV Thakker…
Kidney international, 2000Elsevier
Tubular proteinuria defined by a study of Dent's (CLCN5 mutation) and other tubular
diseases. Background The term “tubular proteinuria” is often used interchangeably with “low
molecular weight proteinuria”(LMWP), although the former implies a definite etiology. A
specific quantitative definition of tubular proteinuria is needed, and we address this by
studying five different renal disorders. Methods Tubular proteinuria was assessed by
measuring urinary retinol-binding protein (RBP), β; 2-microglobulin (β; 2 M), α 1 …
Tubular proteinuria defined by a study of Dent's (CLCN5 mutation) and other tubular diseases.
Background
The term “tubular proteinuria” is often used interchangeably with “low molecular weight proteinuria” (LMWP), although the former implies a definite etiology. A specific quantitative definition of tubular proteinuria is needed, and we address this by studying five different renal disorders.
Methods
Tubular proteinuria was assessed by measuring urinary retinol-binding protein (RBP), β;2-microglobulin (β;2M), α1-microglobulin (α1M), and albumin in 138 patients: 26 affected males and 24 female carriers of the X-linked syndrome “Dent's disease,” 6 patients with other Fanconi syndromes, 17 with distal renal tubular acidosis (dRTA), 39 with glomerulonephritis (GN), and 26 with Chinese herbs nephropathy (CHN).
Results
RBP was better than β;2M or α1M in identifying the tubular proteinuria of Dent's disease. Median urinary RBP levels in mg/mmol creatinine were: affected male Dent's, 18.2, N = 26; carrier female Dent's, 0.30, N = 24; dRTA, 0.027, N = 17; GN, 0.077, N = 39; and normal adults, 0.0079, N = 61. Elevated urinary RBP (>0.017) and albumin < (10 × RBP) + 2 identified all patients with the LMWP of Dent's disease and clearly distinguished their LMWP from that of dRTA and GN. This is a quantitative definition of tubular proteinuria. Consistent with this definition, 80% of those patients with CHN who had an elevated RBP had tubular proteinuria. Urinary RBP and albumin in carriers of Dent's disease were strikingly correlated over a 100-fold range (R = 0.933).
Conclusion
The combination of elevated urinary RBP (>0.017) and albumin < (10 × RBP) + 2 (mg protein/mmol creatinine) is a quantitative definition of tubular proteinuria. Furthermore, our findings suggest that a shared defect in tubular RBP and albumin reuptake causes this form of proteinuria.
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