ESPN 51th Annual Meeting

ESPN 2018


 
A surprising case of acute post-infectious glomerulonephritis
LAURA LUCCHETTI 1 FRANCESCA DIOMEDI CAMASSEI 2 RAFFAELLA LABBADIA 1 MARINA VIVARELLI 1 FRANCESCO EMMA 1

1- DIVISION OF NEPHROLOGY AND DIALYSIS, BAMBINO GESU CHILDREN S HOSPITAL, IRCCS, ROME, ITALY
2- DEPARTMENT OF LABORATORIES, PATHOLOGY UNIT, BAMBINO GESU CHILDREN S HOSPITAL, IRCCS, ROME, ITALY
 
Introduction:

C3 glomerulopathy (C3G) is a new entity secondary to defective control of the complement alternative pathway. Clinical presentation is particularly heterogeneous. The diagnosis of C3G is based on complement level, light and electron microscopy (EM), immunofluorescence (IF) and genetic testing of complement. We describe a case of post-infectious acute glomerulonephritis (PIGN) with classical clinical presentation, and immunofluorescence suggestive of C3G, specifically of dense deposit disease (DDD).

Material and methods:

A 6 year-old boy was referred to our department with a history of macrohematuria and edema for one week. He had a recent history of gastroenteritis with no previous morbidity. His family history was unremarkable for renal diseases. His blood pressure was high. Laboratory investigations revealed hypoalbuminemia, typical proteinogram and lipidogram, normal renal function, anemia, low C3 component with normal C4. Urinalysis showed nephrotic proteinuria with elements of nephritic syndrome (150 erythrocytes/μl). Renal ultrasound was unremarkable. Viral serologic markers excluded any infection. We performed renal biopsy.

Results:

Light microscopy demonstrated diffuse endocapillary and mesangial proliferative glomerulonephritis with 7 crescents/24 glomeruli. A routine IF panel (IgA, IgG, IgM, C1q, C3, C4d, fibrinogen) showed only C3 mesangial and pericapillary positivity with characteristic “mesangial rings”, a picture highly suggestive of DDD (notably, IgG and C4d were negative). Three Methylprednisolone pulses followed by oral prednisone and mycophenolate were given with rapid normalization of proteinuria. However, when available, EM excluded DDD, showing no intramembranous dense deposits but many subepithelial humps, typical finding of PIGN. Confirming diagnosis, C3 level normalized in 4 weeks. All therapy was rapidly interrupted, with no relapses.

Conclusions:

The relevance of this case is that nephrotic proteinuria, proliferative glomerulonephritis and isolated C3 positivity, with characteristic “mesangial rings”, strongly suggested DDD. On the contrary, EM excluded it, allowing the diagnosis of PIGN. In conclusion, EM was essential in making a correct diagnosis, further confirmed by the benign clinical course.