ASSOCIATION OF THIN BASEMENT-MEMBRANE NEPHROPATHY WITH HYPERCALCIURIA, HYPERURICOSURIA AND NEPHROLITHIASIS

Background. Familial persistent microhematuria with normal renal funct ion is the most common presentation of thin basement membrane nephropa thy (TBMN). Gross hematuria episodes and loin pain attacks are other m anifestations of the disease. On the other hand, it has been shown tha t hypercalciuria (HC) and hyperuricosuria (HU) can produce both gross or microscopic non-glomerular hematuria, in addition to their role in renal stone formation. Methods. We studied the prevalence of HC, HU an d nephrolithiasis in a group of 27 biopsy-proven TBMN as well as in 19 non-biopsied first-degree relatives with persistent microhematuria an d 25 first-degree relatives without microhematuria. A group of 27 pati ents with IgA nephropathy (IgAN) and persistent microhematuria, and an other group of 20 healthy subjects without known renal diseases were s elected as control groups. Results. Ten (37%) patients with TBMN and 8 (42%) relatives with microhematuria showed HC and/or HU at presentati on; relatives without microhematuria, IgAN patients and normal control s showed a significantly lower prevalence of HC and HU. The prevalence of previous nephrolithiasis among TBMN patients (25%) was significant ly higher than in IgAN patients (3%; P < 0.05). Family history of neph rolithiasis was recorded in 14 (51%) of the 27 TBMN families, in contr ast with 2 of 27 (7%) with IgAN and 1 of 20 (5%) in normal controls (P < 0.05). The prevalence of nephrolithiasis, gross hematuria bouts and loin pain episodes among TBMN patients and microhematuric relatives s howing HC and/or HU at presentation (44%, 44% and 27%, respectively) w ere significantly higher than those of TBMN patients and microhematuri c relatives with normal calcium and uric acid urinary excretions (10%, 7% and 3%, respectively; P < 0.05). At the end of follow-up (8.8 +/- 4.1 years in TBMN patients and 9.1 +/- 4.2 years in relatives with mic rohematuria), all the cases maintained normal renal function. Conclusi ons. We found a high prevalence of HC, HU, and nephrolithiasis among T BMN patients and relatives with microhematuria. Our study also shows a significant relationship between the presence of HC and/or HU and the prevalence of nephrolithiasis, gross hematuria bouts and loin pain ep isodes.