Glomerular electron-dense deposits in childhood IgA nephropathy

Clinicopathological significance of glomerular capillary IgA deposition in childhood IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is characterized by predominant mesangial IgA deposition. Some patients with IgAN demonstrate IgA deposition in glomerular peripheral capillaries (cap-IgA). The clinicopathological significance of cap-IgA remains incompletely investigated in children.

METHODS

We retrospectively analyzed 503 consecutive cases of biopsy-proven childhood IgAN between July 1976 and June 2013 to compare clinical and pathological features between IgAN patients with and without cap-IgA.

RESULTS

Among the 503 patients, 30 (6.0%) had cap-IgA. We found significant differences in proteinuria (2.0 vs. 0.5 g/day/m², p < 0.0001), time from onset to kidney biopsy (2.2 vs. 8.3 months, p < 0.0001), and rate of proteinuria remission after treatment (23.3% vs. 48.0%, p = 0.007) between both groups. Pathological analysis revealed significant differences in M1 (83.3% vs. 56.0%, p = 0.002), ratio of subendothelial electron dense deposits (EDDs, 58.6% vs. 16.5%, p < 0.0001) and subepithelial EDDs (48.3% vs. 16.5%, p = 0.0001), and glomerular basement membrane (GBM) lysis (58.6% vs. 27.1%, p = 0.0006) between both groups. More than half of cap-IgA patients (17/30, 56.7%), whereas only 26.2% of non-cap-IgA patients (124/473), were treated with immunosuppressive treatments. Six of 30 cases (20%) with cap-IgA reached glomerular filtration rate (GFR) categories G3a-G5 (estimated GFR < 60 ml/min/1.73 m²) at most recent observation (mean observation period: 7.0 ± 4.0 years). According to Kaplan-Meier analysis, patients with cap-IgA had significantly lower kidney survival curves than non-cap-IgA patients (72.8% vs. 97.2% at 10 years, p < 0.0001).

CONCLUSIONS

Cap-IgA is associated with acute inflammation with GBM changes, resulting in refractory heavier proteinuria. Cap-IgA may represent a poor prognostic factor.

Immune profile of IgA-dominant diffuse proliferative glomerulonephritis

The diagnosis of IgA-dominant post-infectious glomerulonephritis (PIGN) may be challenging, as it must be differentiated from that of active IgA nephropathy. Predominant clinicopathologic features of IgA-dominant PIGN substantially overlap with those of active IgA nephropathy. Here, we present a case of a 67-year-old woman with rapidly rising serum creatinine, proteinuria and severe hypertension. The kidney biopsy findings included some features of IgA-dominant PIGN while others were more consistent with classical IgA nephropathy. We describe this patient's immune profile at the time of acute kidney injury and review the literature regarding differentiation of the two entities.

A quantitative analysis of the mesangium in children with IgA nephropathy: sequential study

Quantitative analysis of the mesangial matrix and cells was performed on serial renal biopsies from 41 children with IgA nephropathy. In the repeat renal biopsy, nine patients showed a significant increase of mesangial matrix, 29 showed no change and in three there was a significant decrease. Eight of the nine patients (89 per cent) with a matrix increase had persistent proteinuria at the second biopsy, whereas only 14 of the 32 (44 per cent) without a matrix increase had persistent proteinuria (P less than 0.05). Although the mesangial matrix increased in patients with persistent proteinuria, there was no decrease in patients with clinical remission. In contrast to the mesangial matrix, mesangial cells significantly decreased in 23 patients, did not change in 16, and significantly increased in only two in the second biopsy. These findings suggest that mesangial matrix increase is usually an irreversible change and that persistent proteinuria is associated with matrix increase with worsening in glomerular morphology and clinical outcome. This study indicates the importance of serial renal biopsy in children with IgA nephropathy with persistent proteinuria.

Ultrastructural changes in IgA nephropathy in relation to histologic and clinical data

In order to evaluate the ultrastructural changes in IgA nephropathy (IgAN) and their relationship with light microscopic and clinical features, renal biopsy material from 239 Korean patients with IgAN was studied by light, electron and immunofluorescence microscopy. Forty-one were children and 198 were adults. Modified classification of Meadow et al (1972) for Henoch-Schönlein nephritis was used for the histologic grading of glomerular lesions. Forty-three adults (18%) exhibited histologic grades IV and V lesions in association with more severe clinical findings, when compared to the remaining 196 patients with histologic grades I to III. A significant difference was noted between children and adults in the severity of the glomerular lesions (P less than 0.01). Mesangial deposits were observed in all (100%), subendothelial deposits in 37%, subepithelial deposits in 18%, abnormalities in glomerular basement membrane (GBM) in 20%, mesangiolysis in 44%, and mesangial interposition in 25%. The frequency of GBM abnormalities and subepithelial deposits in children was significantly higher than that seen in adults (P less than 0.01). The abnormalities of GBM were not related to more severe clinical manifestations when our analysis was restricted to grade III histologic lesions. All of the above ultrastructural changes except for mesangial deposits were associated with more severe histologic grading in adults (P less than 0.025 or P less than 0.01). Yet a correlation between these ultrastructural changes and histologic grading could not be studied in children due to confinement of their histology within a more benign group. These results suggest that the five ultrastructural parameters described here appear to bear important prognostic value in adults with IgAN.(ABSTRACT TRUNCATED AT 250 WORDS)

A quantitative study of glomerular basement membrane changes in IgA nephropathy

A quantitative study of glomerular basement membrane (GBM) changes in 16 cases of IgA nephropathy was carried out on two whole glomeruli per case using a wide-field electron microscope. We found that GBM changes are observed more frequently than previously reported, although some changes are small and uneven in distribution. Changes include (a) attenuation, (b) lytic attenuation, (c) garland-shaped widening of the GBM, (d) dome-shaped widening of the GBM, and (e) disruption of the GBM. There was some correlation between the severity of light microscopic findings and the percentage of GBM affected by complicated changes ((b)-(e)). The percentage of complicated GBM changes correlated with the amount of proteinuria at biopsy. The frequent occurrence of GBM changes in IgA nephropathy suggests that they might be playing a role in the pathogenesis of IgA nephropathy.

Mesangial changes in IgA nephropathy in children

The mesangial changes in 92 renal biopsy specimens from 81 children with IgA nephropathy were correlated with the clinical and the other renal biopsy findings. Three types of mesangial changes were identified: mesangial hypercellularity was predominant compared with the increase in matrix in 34 biopsy specimens (type A), the degrees of mesangial hypercellularity and matrix increase were similar in 36 (type B) and matrix increase was predominant in 22 (type C). The interval between the onset of disease and biopsy was significantly shorter in biopsies with type A mesangial changes (P less than 0.01) and significantly longer in those with type C (P less than 0.01). Serial pathologic observations revealed that predominant mesangial hypercellularity was almost exclusively seen in the initial biopsy but predominant matrix increase was usually seen in the follow-up biopsy. The percentage of glomeruli showing sclerosis was significantly higher in biopsies with type C mesangial changes (P less than 0.05). At the latest follow-up, 58% of the patients showing type A and 57% showing type B lost their proteinuria, whereas only 9% showing type C lost their proteinuria (P less than 0.01). These findings suggest that predominant mesangial hypercellularity is characteristic of the early lesion of childhood IgA nephropathy, and progression of disease leads to gradual decrease of mesangial cellularity and increase of matrix with sclerosis.

Clinical course of immunoglobulin A nephropathy in children

The clinical presentation, initial laboratory and renal biopsy findings, and subsequent clinical course of IgA nephropathy were studied retrospectively in 200 children, and findings in those with younger onset and older onset were compared. Eighty-three patients were 8 years of age or younger (group 1) and 117 were 9 years of age or older (group 2) at onset. There were no differences between the two groups with regard to sex, initial renal function, incidence of hypertension and macroscopic hematuria, degree of proteinuria, and pathologic findings. At the latest follow-up, two patients in group 1 and eight in group 2 had chronic renal failure, and five patients in group 1 and 21 in group 2 had heavy proteinuria with or without hypertension (P less than 0.01), whereas 36 (43%) patients in group 1 and 29 (25%) in group 2 had normal urine, blood pressure, and glomerular filtration rate (P less than 0.01); the disease followed a significantly more benign course in children with younger onset than in those with older onset. These observations suggest some age-related differences in the natural history of childhood IgA nephropathy.

Immunoelectron microscopic study of childhood IgA nephropathy and Henoch-Schönlein nephritis

Renal biopsy specimens from 11 children with Henoch-Schönlein nephritis and 14 with IgA nephropathy were examined by immunoelectron microscopy. The distribution of IgA reaction product (RP) was found to be similar to that of the electron-dense deposits seen with conventional electron microscopy. Deposits of IgA-RP were present in the mesangium and in the subendothelial region of the peripheral glomerular capillary wall in all patients. Subepithelial deposits of IgA-RP were seen in 12 patients. Deposits of IgG-RP were rare and no deposits of IgM-RP were observed. Deposits of C3-RP were found frequently, although they were smaller and less extensive than deposits of IgA-RP. There was no significant difference between Henoch-Schönlein nephritis and IgA nephropathy with regard to immunoelectron microscopy findings. These observations suggest that Henoch-Schönlein nephritis and IgA nephropathy are both forms of mesangiopathic glomerulo-nephritis caused by immune complexes, mainly composed of IgA.

Lysis of the glomerular basement membrane in children with IgA nephropathy and Henoch-Shönlein nephritis

An electron-microscopic study of the glomerular basement membrane was made on 242 renal biopsies from 222 children with a variety of renal diseases. Lysis of the basement membrane was observed in 16 of the 25 children with Henoch-Schönlein nephritis, 36 of the 72 with IgA nephropathy and one with acute poststreptococcal glomerulonephritis. Lysis was frequently associated with subepithelial dense deposits and polymorphonuclear leukocytes, and these are thought to play a role in the lytic process. There was a significant correlation between the presence of lysis of the basement membrane, the degree of proteinuria and the severity of glomerular changes by light microscopy. These findings suggest that the degree of lysis is an indication of the severity of the disease and lysis is associated with progressive disease and a worse prognosis in Henoch-Schönlein nephritis and IgA nephropathy.

Focal segmental glomerulosclerosis with and without nephrotic syndrome in children

The clinical presentation, initial laboratory and renal biopsy findings, and course of focal segmental glomerulosclerosis (FSGS) were studied retrospectively in 57 children in order to compare findings in those with and without nephrotic syndrome and to establish factors of prognostic significance. All patients had proteinuria. Eleven patients were otherwise asymptomatic, and nephrotic syndrome did not develop (group 1); 14 patients had asymptomatic proteinuria, but nephrotic syndrome subsequently developed (group 2); 32 patients had nephrotic syndrome (group 3). There were no differences between these three groups with regard to sex, age, initial renal function, incidence of hypertension and hematuria, and pathologic findings. At the latest follow-up, five group 1 patients, six in group 2, and 14 in group 3 had chronic renal failure; the incidence was similar for those with asymptomatic proteinuria and those with nephrotic syndrome. The location of the sclerosis within the glomerulus proved to have prognostic significance. All 12 patients with peripheral FSGS maintained normal renal function, whereas in 25 of the 44 with hilar FSGS chronic renal failure developed.