Eculizumab as a New Treatment for Severe Acute Post-infectious Glomerulonephritis: Two Case Reports

C3 glomerulopathy associated with mycoplasma pneumoniae infection and positive IgA staining

BACKGROUND

Patients with C3 glomerulopathy (C3G) often have a history of infection, which implies that infection may lead to abnormal activation of the complement alternative pathway (CAP) and induce the development of C3G. However, patients with postinfectious glomerulonephritis (PIGN) often have a low serum C3 concentration and positive glomerular C3 staining, consistent with the activation of the CAP. PIGN, especially if it involves simultaneous IgA deposition, is often difficult to differentiate from C3G.

CASE PRESENTATION

In this study, we report the consequences of Mycoplasma pneumoniae (MP) infection in a 66-year-old male Chinese patient, who developed persistent hypocomplementemia, gross hematuria, and rapidly progressive glomerulonephritis. The findings of the histologic examination of an initial renal biopsy were consistent with a diagnosis of IgA-dominant postinfectious glomerulonephritis. The sample was negative for Gd-IgA1 staining. After treatment with antibiotics, glucocorticoids, and mycophenolate mofetil, the patient's serum creatinine decreased from a peak of 387 µmol/L to 195 µmol/L prior to discharge, and there was a partial response in his urinary protein concentration. After 2 months, his serum C3 concentration had returned to normal. However, owing to reinfection with MP the patient's serum creatinine rapidly increased again to 475.07 µmol/L, and this was accompanied by a decrease in serum C3 concentration (> 8 months) and positivity for C3 nephritis factor. Examination of both renal biopsies showed stronger immunostaining for C3 than for IgA in the glomeruli.

CONCLUSION

Thus, MP infection can cause sustained activation of the CAP, leading to C3G. For patients with MP infection, if there is an ongoing decrease in complement C3 levels and a progressive increase in serum creatinine, it is crucial to be vigilant for possible C3G and to consider the use of immunosuppressive therapy in conjunction with anti-infective treatment to prevent the ongoing activation of the CAP.

Acute Postinfectious Glomerulonephritis

Postinfectious glomerulonephritis (PIGN) is a leading cause of acute glomerulonephritis in children. The presentation of PIGN can vary from asymptomatic microscopic hematuria incidentally detected on routine urinalysis to nephritic syndrome and a rapidly progressive glomerulonephritis. Treatment involves supportive care with salt and water restriction, and the use of diuretic and/or antihypertensive medication, depending on the severity of fluid retention and the presence of hypertension. PIGN resolves completely and spontaneously in most children, and the long-term outcomes are typically good with preserved renal function and no recurrence.

The Rational Use of Complement Inhibitors in Kidney Diseases

The development of complement inhibitors represented one of the major breakthroughs in clinical nephrology in the last decade. Complement inhibition has dramatically transformed the outcome of one of the most severe kidney diseases, the atypical hemolytic uremic syndrome (aHUS), a prototypic complement-mediated disorder. The availability of complement inhibitors has also opened new promising perspectives for the management of several other kidney diseases in which complement activation is involved to a variable extent. With the rapidly growing number of complement inhibitors tested in a rapidly increasing number of indications, a rational use of this innovative and expensive new therapeutic class has become crucial. The present review aims to summarize what we know, and what we still ignore, regarding complement activation and therapeutic inhibition in kidney diseases. It also provides some clues and elements of thoughts for a rational approach of complement modulation in kidney diseases.