Dr Isra Iftikhar1, Dr Zhan Lim, Dr Vino JAYARAMAN KAVARTHAPOL
1Fiona Stanley Hospital, Harrisdale, Australia
Biography:
Second year Renal Trainee with special interest in GN. Mum of 4, cooking is the hobby.
Background:
We present a challenging case of C3-dominant crescentic glomerulonephritis with minimal treatment response, underscoring the difficultly in distinguishing between C3 glomerulopathy (C3G) from infection-related GN (IRGN).
Case Presentation:
78-year-old female presented with lower limb cellulitis with fever and rigors on a background of Parkinson disease, type II diabetes, hypertension, and obesity. Initial evaluation revealed raised inflammatory markers, normal kidney function (creatinine 53 umol/L, eGFR 87) and Bland urine. Urine cultures grew Escherichia Coli, and wound cultures isolated Staphylococcus aureus and Group C streptococcus.
Despite broad spectrum antibiotics, she developed a vasculitic rash in lower limbs and severe acute kidney injury with haematoproteinuria (urine ACR 316). Immunological evaluation showed normal serum complements (C3 1.25 g/L, C4 0.16 g/L), elevated anti-streptolysin-O titre at 3450 IU/mL (ref <200) and normal anti-DNase B. Autoantibodies including ANA, ANCA, dsDNA, PLA2R, anti-GBM antibodies, and serum electrophoresis were negative.
She received pulse methylprednisolone and required dialysis for oliguria. Kidney biopsy demonstrated diffuse crescentic glomerulonephritis with 95% cellular crescents and focal endocapillary hypercellularity. Immunofluorescence revealed dominant mesangial C3 deposits with minimal IgG staining. Complement studies showed weakly positive C3 nephritic factor with normal CH50 and AH50 levels. Genetic testing for complement dysregulation was pending. Despite ongoing corticosteroid treatment, the patient remained dialysis dependent. Repeat biopsy was deferred due to comorbidities, advanced frailty, and minimal renal recovery.
Conclusion:
C3-dominant glomerulonephritis poses a significant diagnostic challenge to distinguish between C3G and IRGN due to overlapping histological features. While genetic studies for complement dysregulation can provide further diagnostic clarity, their utility may be limited by extended turnaround time. A multi-disciplinary approach is essential for evaluating these complex cases, which often carry a poor prognosis.