| Abstract|| |
Mesangial IgG glomerulonephritis (MesIgGN) is recently recognized as a distinct type of glomerulonephritis. In our renal biopsy series, two patients with MesIgGN were identified. The morphologic criteria detected in these patients included mesangial dense deposits by ultrastructural studies, which were predominantly positive for IgG by immunofluorescence. Both patients were young boys, one presented with hematuria and the other with the nephrotic syndrome. Similar cases have been reported in other studies from around the world; however, this is the first report of MesIgGN from Saudi Arabia.
|How to cite this article:|
Jalalah SM. IgG glomerulonephritis: A morphologic study of a rare entity. Saudi J Kidney Dis Transpl 2009;20:798-801
| Introduction|| |
Mesangial IgG glomerulonephritis (MesIgGN) is a rare form of glomerulonephritis (GN). It has been recently recognized as a distinct entity characterized by mesangial deposits, predominantly positive for IgG. The entity of MesIgGN was first reported by Sato et al.  Subsequently, few other reports have emerged defining this new form of GN morphologically and clinically. ,
This is the first report from Saudi Arabia describing the morphology of MesIgGN from a single center in the country.
| Subjects and Methods|| |
All renal biopsies performed in patients with primary GN (n = 598) from 1988 to 2007 at the College of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia were reviewed. Cases with unclassifiable GN with predominant mesangial IgG deposits were selected and two patients with these criteria were identified. Lupus nephritis was excluded on clinical grounds in both these patients.
All renal biopsies were examined by light microscopy, immunofluorescence and electron microscopic studies using the routine standard techniques. For light microscopic studies, paraffin embedded tissue sections were stained with hematoxylin and eosin (H&E), periodic acid Schiff (PAS), John's methanamine silver (JMS) and trichrome stain. For immunofluorescence studies, frozen renal tissue sections were directly labeled with fluorescein isothiocyanate (FITC) conjugated antibodies against IgG, IgA, IgM, C3, C4, C1q and fibrinogen. Tissue submitted for electron microscopic studies was processed into resin embedded blocks; ultrathin sections were stained with uranyl acetate and lead citrate and examined by Philips transmission electron microscope CM100.
| Results|| |
There were two patients with IgG predominant GN in our series representing 0.3% of the primary GN in our renal biopsy archive. The first patient was a four year old boy who presented with the nephrotic syndrome. The second patient was a 14 year old boy who presented with hematuria.
The results of the renal biopsy studies are as follows:
Light microscopic examination
The glomeruli in both patients show mild mesangial changes with variable degree of mesangial matrix expansion [Figure 1]A,[Figure 1]B. Case-2 demonstrated mild focal mesangial cell increase [Figure 1]B. The glomerular capillary wall did not show obvious abnormalities. In both cases, glomerular sclerosis was absent and no inflammation was detected.
The glomeruli in both cases demonstrated diffuse granular mesangial reaction predominantly with labeling for IgG (2+ to 3+) [Figure 2]A and [Figure 2]B. Less intense mesangial reaction was demonstrated for IgM (trace to 1+) in both cases, whereas positive labeling for C3 (1+) was seen only in case-2. Negative results were obtained in both cases with labeling for IgA, C4, and C1q.
Electron microscopic findings
The most prominent finding revealed by the ultrastructural studies in both cases was the presence of large dense deposits in the mesangial area [Figure 3]A and [Figure 3]B. There were no deposits in sub-endothelial or sub epithelial locations.
| Discussion|| |
MesIgGN has recently been recognized as a distinct entity. The current study presents the first report of MesIgGN from Saudi Arabia; no similar cases have been reported in the literature from this part of the world.
The first report recognizing MesIgGN as a distinct entity was published in 1993 by Sato et al.  Since then, a few reports have accumulated in the literature of similar cases describing the morphologic criteria, clinical features and outcome of these patients. Results of these studies have confirmed that MesIgGN does actually represent a different type of GN, which needs to be recognized by clinicians and pathologists. ,,, The basic criteria for diagnosing MesIgGN are the presence of mesangial dense deposits which are predominantly positive for IgG; these patients should not have any evidence of systemic diseases such as systemic lupus erythematosus.
Evidence for MesIgGN being a distinct type of GN arises from morphologic studies of serial biopsies from the same patients, which have demonstrated that MesIgGN does not show any morphologic change over a long period of followup. Also, the mesangial deposits persisted. ,
These results indicate that MesIgGN starts as a distinct type of GN and does not evolve into another type over time. Moreover, symptomatic recurrence of MesIgGN in allograft kidneys has been reported in two patients in two different studies; this finding was an additional evidence to prove that MesIgGN is a specific and distinct entity. ,
Morphologically, MesIgGN is similar to IgA nephropathy and IgM nephropathy; all three types show mesangial involvement with immune complex deposits in patients with primary GN. The difference between these entities is in the type of immunoglobulin deposited in the mesangium, which makes each of these messangial GN a distinct type morphologically.
The two patients described in this study demonstrated the same morphologic features indicated in the other studies, consisting mainly of mesangial dense deposits positive for IgG only in one case, and accompanied by IgM and C3 in the other case. The morphology in these two patients did not show any evidence of chronic changes in the biopsy.
The clinical presentation of MesIgGN includes a wide range of features including proteinuria, hematuria, the nephrotic syndrome and gross hematuria, and sometimes chronic renal failure. Also, the age at presentation varies from young children to elderly over 70 years. Most cases reported from Japan presented with hematuria and few with proteinuria. ,, The patients in the current study were both male children with different clinical presentations; one presented with the nephrotic syndrome and the other with hematuria, but both had normal renal functions. The frequency of occurrence of MesIgGN is very low in all studies; similarly, in our study, MesIgGN was rare and accounted for 0.3% of all biopsy proven-primary GN.
Although the number of cases with MesIgGN reported in the literature is small [Table 1], comparison of patients' results from different parts of the world demonstrated some differences in the clinical presentation and behavior of the disease. The distribution of the reported cases seems to be concentrated in Japan from where most studies are published; ,, no other Asian countries have similar case reports in the literature. In the Japanese studies, the patients' followup indicated that most MesIgGN cases have a benign clinical course. On the contrary, fewer cases of MesIgGN were reported from France and most of these patients developed chronic renal disease.  This discrepancy in the prognosis between the two populations could not be correlated with the patient's age at onset of symptoms, or the duration of the disease. Accordingly, it can be postulated that the nature and course of MesIgGN is different among human races and hence its outcome and prognosis is different.
In conclusion, there is sufficient evidence currently to support that MesIgGN is a distinct type of GN. This entity is very rare; however, nephrologists and pathologists should be aware of its existence especially because some reports indicate that it may carry a less favorable course and prognosis. Recognition of larger number of cases with longer duration of follow-up is needed to understand the pathogenesis of MesIgGN and help in designing the management for this group of patients.
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Sawsan M Jalalah
Department of Pathology, College of Medicine, King Abdulaziz University, P.O. Box 512, Jeddah 21442
[Figure 1], [Figure 2], [Figure 3]