Glomerular mesangial fibrillary deposits in a patient with diabetes mellitus

Ultrastructural Examination of Glomerular Fibrillary Deposits in Diabetic Nephropathy

Glomerular fibrillary deposits have occasionally been reported in diabetic nephropathy, but no large-scale, ultrastructural evaluation of these deposits has been reported so far. Here, we report our study of glomerular non-Congophilic, DnaJ homolog subfamily B member 9 negative fibrillary deposits in diabetic nephropathy as characterized by transmission electron microscopy. Clinical data from 55 patients with biopsy-confirmed diabetic nephropathy and 18 healthy living donors were reviewed, and their biopsies were evaluated by light microscopy, immunofluorescence, and electron microscopy. Small fibrillary structures with a diameter of 10 ± 1 nm were present in all cases with diabetic nephropathy, regardless of the histologic class. In addition, glomerular fibrillary structures with a diameter of 23 ± 5 nm or 30 ± 7 nm were present in 35 cases. Interestingly, especially the small- and medium-sized fibrils, usually without apparent organization, were comparable with fibrils in fibrillary glomerulopathy. We conclude that glomerular fibrillary deposits occur far more commonly in renal biopsies of patients with diabetic nephropathy than generally considered. This is an important finding because their similarity to fibrils in fibrillary glomerulonephritis may complicate the histologic diagnostic process, especially in cases of overlapping clinical manifestations. Therefore, when encountering fibrillary deposits on electron microscopy, it is important to consider diabetic nephropathy as an alternative diagnosis.

Monoclonal immunoglobulin-associated proliferative glomerulonephritis characterized by organized deposits of striated ultra-substructures: A case report

We herein report the case of a 64-year-old male who presented with progressive glomerulonephritis notable for organized and striated ultra-substructures. The patient was diagnosed with hypertension and proteinuria 3 years prior to admission and subsequently developed nephrotic syndrome and impairment of renal function. Laboratory tests did not reveal any evidence of infections or autoimmune diseases. Monoclonal gammopathy was not detected in serum or urine, although a small population of abnormal plasma cell clones was detected by flow cytometry. A renal biopsy showed mesangial and endocapillary proliferative glomerulonephritis with lobular accentuation, accompanied with focal and segmental double-contour formation. Additionally, moderate tubulointerstitial scarring and arteriosclerosis were noted. Immunofluorescence staining revealed positive staining for IgG, IgM, C3, C1q, and fibrinogen. IgG subclass and light chain staining showed restricted positivity for IgG1κ. Electron microscopy demonstrated massive amounts of subendothelial deposits with a fibrillary and branching profile. At higher magnification, a periodic striated pattern was observed within the microfilament-like structures. Immunohistochemical staining was negative for myoglobin, laminin, and collagens (type III and IV). Steroid and antihypertensive therapy did not show improvement in renal function. The second biopsy performed 2 years later revealed a similar lobular proliferative glomerulonephritis pattern with more extensive tubulointerstitial damage, indicating poor response to immunosuppressive therapy. The patient progressed to end-stage renal disease and required hemodialysis. We discuss the possible origins of the deposits with unusual substructures observed in this case.

Renal diseases with organized deposits: an algorithmic approach to classification and clinicopathologic diagnosis

CONTEXT

Most renal diseases with organized deposits are relatively uncommon conditions, and proper pathologic characterization determines the specific diagnosis. Different entities with specific clinical correlates have been recognized, and their correct diagnosis has an impact on patient management, treatment options, and determination of prognosis.

OBJECTIVE

The diagnosis of these conditions depends on careful evaluation of the findings by light microscopy together with immunofluorescence and electron microscopy. The objective of this manuscript is to delineate an algorithmic approach helpful in the pathologic assessment of these conditions at the light microscopic level. In some diseases, the immunomorphologic parameters short of electron microscopy provide solid information to suggest or make a definitive diagnosis. Nevertheless, electron microscopy plays a crucial role, because the criteria to separate these entities often are heavily influenced by the electron microscopic findings. Accepted diagnostic criteria for each of these conditions are discussed.

DESIGN

Information used for this manuscript is gathered from published data and the authors' experience.

RESULTS

The most common of these conditions is amyloidosis, which may account for as many as 5% to 8% of all renal biopsies in some renal pathology practices. Fibrillary, immunotactoid, and cryoglobulinemic glomerulopathies together represent, at most, 1% of all renal biopsies performed for medical renal diseases. Diabetic fibrillosis also is uncommon. Glomerulopathies associated with fibronectin deposits and collagenofibrotic glomerulopathy are extremely rare.

CONCLUSIONS

A systematic, algorithmic approach to the evaluation of the renal biopsies from patients with these disorders is very helpful to rule out certain conditions in the early stages of the evaluation of the biopsies. However, it is not uncommon for the final definitive diagnosis to be reached only after electron microscopic evaluation.