La tunisie Medicale - 2018 ; Vol 96 ( n°07 ) : 442-444
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Résumé

Introduction:
Les dépôts glomérulaires sont une caractéristique pathologique majeure d'une large gamme de néphropathies glomérulaires et peuvent être situés dans les régions mésangiale, sous-épithéliale et sous-endothéliale. Des cas rares de glomérulopathies primitives définis par des dépôts mésangiaux exclusifs ou prédominants d’IgG ont été signalés.
Méthodes:
Nous avons examiné les résultats de 848biopsies rénales pratiquées dans notre département entre 2007 et 2016, on a trouvé un seul cas de glomérulopathie primitive à dépôts mésangiaux d’IgG en l'absence de toute preuve de lupus érythémateux systémique, d'autres maladies systémiques ou d’infections.
Case report:
Patient de sexe masculin âgé de 55 ans consulte pour des œdèmes. A la biologie, il avait un syndrome néphrotique avec hématurie. Le taux de créatinine était à 88 µmol/l. Il ne présentait pas de syndrome inflammatoire biologique.  IL a bénéficié d’une ponction biopsie rénale concluant à des dépôts mésangiaux exclusifs d’IgG sans lésions prolifératives. Le bilan immunologique était sans anomalies durant toute la période de suivi. Les sérologies: HVB, HVC étaient négatives. Le patient était alors mis sous corticothérapie à pleine dose (1mg/Kg/j). L’évolution était marquée par une rémission complète atteinte après 3mois du début du traitement. Au cours du suivi, le patient a présenté 3 rechutes du syndrome néphrotique en 3 ans sans facteur de décompensation évident. La décision était alors de mettre le patient sous Mycophénolate mofétil (MMF) avec une rémission complète atteinte après 2 mois.
Conclusion:
La néphropathie glomérulaire à dépôts mésangiaux d’IgG est un type de glomérulopathie primaire très rare mais distinct.

Mots Clés
Article

PRIMARY GLOMERULONEPHRITIS WITH PREDOMINANT MESANGIAL IMMUNOGLOBULIN G DEPOSITS

Introduction:
Glomerular deposits are a major pathologic feature of a wide range of human glomerulonephritis and may be located in the mesangial, subepithelial, and subendothelial regions. Rare cases of primary glomerulonephritis defined by exclusive or predominant mesangial IgG deposits were reported.

Aim:
We reviewed the pathologic findings for the 848 renal biopsies examined in our departement between 2007 and 2016, a case of primary mesangial IgG glomerulonephritis (MIG) in the absence of any evidence of systemic lupus erythematous (SLE), infections or other systemic disease was found.

Reported case:
Male patient aged 50 years consults for nephrotic syndrome (proteinuria=7g/1.73m2/ day, Albuminemia=14g/l, Protidemia=31g/l) with hematuria. The serum creatinine concentration was 88 µmol/l, and the creatinine clearance was on MDRD at 82 ml/min/1.73m2. The hemoglobin level was 12 g/dl. He had no inflammatory biological syndrome.
The results of the renal biopsy studies are as follows:  (Figure 1), (Figure 2).

Figure 1: Mesangial proliferation

Figure 2 : Turgescent podocytes
Light microscopic examination: The glomeruli showed mild me¬sangial changes with variable degree of mesan¬gial matrix expansion. The glomerular capillary wall was thickened with reduction of their light but without thrombosis.
 Immunofluorescence study showed in the glomeruli di¬ffuse granular mesangial reaction predominantly with labeling for IgG.Very less intense mesangial reaction was demonstrated for C3. Negative results were obtained with labeling for IgA, IgM, and C1q.
CH50, C3 and C4 levels were normal and antinuclear antibody and anti-DNA antibody assays remained negative during the follow-up period. A full dose corticosteroid was initiated
(1mg/ Kg/ day). The interval from onset of steroid therapy to remission of nephrotic syndrome was 2 months. Later and during follow-up; the patient had developed 2 relapsing nephrotic syndrome episods without obvious decompensation factors. The first episode was at 12 months and treated by corticosteroid with remission after one month. The second episode of relapse was at 5 years after the diagnosis. The patient was switched to Mycophenolate mofetil with remission after 2 months. The duration of the total follow-up is 6 years.

Discussion:
Glomerular mesangial IgG deposition occurs in various types of primary and secondary glomerulonephritis, including lupus nephritis and mesangiocapillary nephropathy. In   Immunoglobulin A (IgA) nephropathy, the most common type of primary glomerulonephritis, IgG (mainly IgG1 and IgG3) is codeposited with IgA in up to 40% of cases. In our case, there was no IgA deposit; so IgA nephropathy was eliminated.
The recognition of this disease as a new type of glomerulonephritis requires the careful exclusion of other types of glomerulonephritis. There was no marked mesangial cell proliferation in any case.  No clinical or biologic features of ongoing infection were noted for any patient during extended follow-up monitoring. Marked mesangial proliferation and low complement levels, two main features of postinfectious glomerulonephritis, were absent in our case.
Although the number of cases with MIG reported in the literature is small (Table 1), com-parison of patients' results from different parts of the world demonstrated some differences in the clinical presentation and behavior of the di¬sease. The distribution of the reported cases seems to be concentrated in Japan from where most studies are published like in the report of Yoshikawa (2) concerning 10 pediatric cases of MIG and in the report of Sato (1) concerning adult cases of MIG.  In the Japanese studies, the patients' follow¬up indicated that most MIG cases have a benign clinical course with a relatively benign course of MIG after a median follow-up period of 4.9 years. On the contrary, fewer cases of MIG were reported from France and most of these patients developed chronic renal disease (3). Then was reported the largest series of MIG cases to date by Fadi Fakhouri at Hôpital Necker, including 14 cases in wich the course of MIG was far from benign, in as much as chronic renal failure occurred in one-half of the patients. Treatment was purely supportive and consisted of an antihypertensive and/or antiproteinuric regimen in 5 patients. Moreover, symptomatic recurrence of MIG in allograft kidneys has been reported in two patients in two different studies; this finding was an additional evidence to prove that MIG is a specific and distinct entity. In the report by Yoshikawa et al. (2, four children with MIG, nephrotic syndrome, and normal renal function were treated with a corticosteroid regimen, with complete or partial remission in two cases. In a case report, nephrotic syndrome related to MIG may be resistant to corticosteroid and cyclophosphamide (5).
The evolution of our patient is different from that reported in the literature; he initially received a full dose corticosteroid. As he had developed 2 relapsing nephrotic syndrome episods, he was switched to Mycophenolate mofetil with remission after 2 months. No clinical kidney disease was noted after a total follow up of 6 years.


Conclusion:
 In conclusion, there is sufficient evidence cur¬rently to support that MIG 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 MIG and help in designing the management for this group of patients.

Table 1: Mesangial IgG glomerulonephritis: Reports in the literature

Author

Year

Nb of patients

Age (years)

Country

Sato M et al 1

1993

6

6- 52

Japan

Yoshikawa N et al 2

1994

10

Children

Japan

Kano K et al 4

1996

1

8

Japan

Sepandj F 5

1998

1

48

Canada

Onitsuka et al 6

2000

1

48

Japan

Fakhouri F et al 3

2002

14

13-47

France

Assadi FK 7

2004

1

17

USA

Sawsan M Jalalah 8

2009

2

4   16

Saudi Arabia

Present study

2017

1

50

Tunisia

Références
  1. Sato M, Kojima H, Nabeshima K, Nakajima Y, Koshikawa S. Primary glomerulonephritis with pre¬dominant mesangial immunoglobulin G deposits a distinct entity? Nephron 1993;64:122-8
  2. Yoshikawa N, Iijima K, Shimomura M, Nakamura H, Ito H. IgG-associated primary glomerulonephritis in children. Clin Nephrol 1994;42:281-7.
  3. Fakhouri F, Darre S, Droz D, et al. Mesangial IgG glomerulonephritis: a distinct type of primary glome¬rulonephritis. J Am Soc Nephrol 2002;13:379-87.
  4. Kano K, Ueda Y, Iidaka K, Ichimura T. Glomerulo¬nephritis with predominant paramesangial IgG deposition. Pathol Int 1996;46:306-9
  5. Sepandj F, McFarlane C, Trillo A. Nephrotic syndrome secondary to primary immunoglobulin-G mesangioproliferative glomerulonephritis. Nephrol Dial Transplant 1998;13:1889-90.
  6. Jalalah SM. IgG glomerulonephritis : A morphologic study of a rare entity. Saudi J Kidney Dis Transpl 2009 ; 20 :798-801
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