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Abstract titles should be brief and reflect the content of the abstract.
Horseshoe kidney (HK) is the most common congenital renal fusion anomaly (≈1 in 400–600 births). Although primarily a structural defect, HK may predispose to or coexist with glomerular diseases such as focal segmental glomerulosclerosis (FSGS). Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) causes pauci-immune crescentic glomerulonephritis and represents a therapeutic challenge. We report the first documented case of the triad: HK, AAV, and FSGS, featuring a technically successful biopsy in HK and long-term rituximab maintenance therapy.
A 67-year-old man with a five-year history of recurrent systemic manifestations and previously inadequate treatment was referred for evaluation of edema, dyspnea, and hemoptysis. Serology revealed c-ANCA positivity (1:640), normal complement levels, and negative ANA, dsDNA, and anti-GBM antibodies. Imaging identified a horseshoe kidney. Ultrasound-guided percutaneous biopsy from the lower pole of the HK was technically challenging but completed successfully without complications.
Histology: 9/12 glomeruli were globally sclerosed, one contained a fibrous crescent, and one showed segmental sclerosis. The interstitium displayed a 35–40% lymphoplasmacytic infiltrate and >20% interstitial fibrosis/tubular atrophy. Immunofluorescence revealed a pauci-immune pattern. Final diagnosis: ANCA-associated pauci-immune crescentic glomerulonephritis with concomitant FSGS in a horseshoe kidney.
Following biopsy confirmation, the patient received pulse methylprednisolone 500 mg IV daily for 3 days, followed by oral corticosteroids and rituximab 500 mg × 2 for induction. Maintenance rituximab was administered at months 6, 12, and 18 per the MAINRITSAN protocol. At last follow-up: serum creatinine 157 µmol/L, albumin 37 g/L, hemoglobin 138 g/L, with no proteinuria or hematuria.
This unique case represents the first reported constellation of horseshoe kidney, ANCA-associated vasculitis, and FSGS. It underscores that congenital renal anomalies may predispose to or modify autoimmune glomerular disease via altered hemodynamics and ischemic stress. Percutaneous biopsy of HK, though technically demanding, is safe and essential for diagnostic accuracy. Long-term remission achieved with rituximab-based therapy after delayed recognition highlights the importance of early diagnosis and multidisciplinary management in complex renal pathology.
