Familial lobular glomerulopathy: first case report in Asia

Clinicopathologic Features and Outcomes in Fibronectin Glomerulopathy: A Case Series of 19 Patients

Aims: To describe the characteristics and prognosis of 19 patients with fibronectin glomerulopathy (FNG) and evaluate prognostic factors associated with poor renal outcomes.

Methods: Included in this retrospective study was 19 FNG patients in Nanjing Glomerulonephritis Registry system. Associations between the clinical parameters, pathological features, and renal outcomes were evaluated by Kaplan-Meier survival analysis.

Results: Of the 19 FNG patients included in this study, 8 (42.1%) were women. The median age of the 19 FNG patients was 31 (17–71) years, and the median disease duration 48 (1–175) months at diagnosis. At the time of renal biopsy, the mean serum creatinine (Scr) was 1.22 ± 0.16 mg/dl and urinary protein was 6.24 ± 0.97 mg/24 h. Renal biopsy showed a lobular appearance with cellular mesangial nodules expanded by matrix in 14 cases. After a median follow-up period of 87 months (interquartile range 34–114.5 months), 8 FNG patients developed renal function decline, including 7 progressing into end-stage renal disease (ESRD) and 1 presenting with by a 2-fold-increase in Scr. Scr and proteinuria remained stable in the remaining 11 patients. Kaplan-Meier survival analysis showed that nephrotic range proteinuria (P = 0.022) and focal glomerular sclerosis (P = 0.028) were associated with renal function decline.

Conclusions: Nephrotic range proteinuria and focal glomerular sclerosis were associated with renal function decline during the follow-up period of the FNG patients in our series. FNG Patients at risk of renal function decline should be identified preferentially and given more progressive and effective therapies to prevent further disease progression.

Fibronectin glomerulopathy complicated with persistent cloaca and congenital esophageal atresia: a case report and literature review

BACKGROUND

Fibronectin glomerulopathy is a rare, inherited, autosomal dominant, glomerular disease characterized by proteinuria, microscopic hematuria, hypertension, massive glomerular deposits of fibronectin, and slow progression to end-stage renal failure. Because the incident of fibronectin glomerulopathy is extremely low, the pathophysiology, genetic abnormalities, epidemiology, and mechanisms remain to be elucidated.

CASE PRESENTATION

We report a 21-year-old woman with fibronectin glomerulopathy, who had been diagnosed with persistent cloaca and congenital esophageal atresia at birth. She developed proteinuria and hematuria 7 months before admission. Urinary protein and serum creatinine levels were 3.38 g/gCr and 0.73 mg/dL. Renal biopsy showed severe mesangial widening due to massive deposits, which was positive periodic acid-Schiff and negative methenamine silver. Immunostaining was negative for immunoglobulin but positive for fibronectin. Electron microscopy showed diffuse mesangial granular deposits. Thus she was diagnosed with fibronectin glomerulopathy, despite a negative family history of kidney disease and lack of any known missense mutations of fibronectin 1 gene.

CONCLUSION

We report a patient who developed fibronectin glomerulopathy during the clinical course of extremely rare congenital malformations, including persistent cloaca and congenital esophageal atresia. We describe a case of this condition in detail and summarize the 75 case reports of fibronectin glomerulopathy.

Fibronectin glomerulopathy

Fibronectin glomerulopathy occurs between the second and fifth decades of life in most patients, and it is known to be slowly progressive with mild proteinuria leading to kidney failure. The case of a 78-year-old woman with a rapid course of nephrotic syndrome due to fibronectin glomerulopathy is reported. She had proteinuria that rapidly increased to 6.8 g/day in a month and microscopic haematuria. A renal biopsy specimen showed lobular glomerulopathy and membranoproliferative glomerulonephritis-like lesions on light microscopy. There was scanty staining for immunoglobulins and complement. Electron microscopy revealed granular deposits with fibril formation. Immunohistochemistry of the fibronectin showed intense staining in the mesangium and peripheral loop. Therefore, this case was diagnosed as fibronectin glomerulopathy. The kidney function was rapidly decreasing, necessitating haemodialysis 2 months after renal biopsy. It is important to consider fibronectin glomerulopathy in the differential diagnosis of nephrotic syndrome in older people.

Mutations in FN1 cause glomerulopathy with fibronectin deposits

Glomerulopathy with fibronectin (FN) deposits (GFND) is an autosomal dominant disease with age-related penetrance, characterized by proteinuria, microscopic hematuria, hypertension, and massive glomerular deposits of FN that lead to end-stage renal failure. The genetic abnormality underlying GFND was still unknown. We hypothesized that mutations in FN1, which encodes FN, were the cause of GFND. In a large Italian pedigree with eight affected subjects, we found linkage with GFND at the FN1 locus at 2q32. We sequenced the FN1 in 15 unrelated pedigrees and found three heterozygous missense mutations, the W1925R, L1974R, and Y973C, that cosegregated with the disease in six pedigrees. The mutations affected two domains of FN (Hep-II domain for the W1925R and the L1974R, and Hep-III domain for the Y973C) that play key roles in FN-cell interaction and in FN fibrillogenesis. Mutant recombinant Hep-II fragments were expressed, and functional studies revealed a lower binding to heparin and to endothelial cells and podocytes compared with wild-type Hep-II and an impaired capability to induce endothelial cell spreading and cytoskeletal reorganization. Overall dominant mutations in FN1 accounted for 40% of cases of GFND in our study group. These findings may help understanding the pathogenesis of proteinuria and glomerular FN deposits in GFND and possibly in more common renal diseases such as diabetic nephropathy, IgA nephropathy, and lupus nephritis. To our knowledge no FN1 mutation causing a human disease was previously reported.