Beyond Oral Anticoagulants Two case reports of Biopsy-Proven Heparin-Induced Anticoagulant-Related Nephropathy

Introduction: Anticoagulant-Related Nephropathy (ARN) is an emerging and often unrecognized form of acute kidney injury. Histologically characterized by glomerular hemorrhage and intratubular erythrocyte casts, ARN is a serious complication associated with increased morbidity and progression to chronic kidney disease. Although it has been described in association with oral anticoagulants, the literature regarding ARN induced by non-oral agents, such as low molecular weight heparin (LMWH), remains extremely scarce. This report aims to fill this gap, highlighting the importance of early diagnosis in complex clinical settings. Case presentations: We present two cases of biopsy-proven ARN induced by LMWH in patients with concomitant active renal disease. The first case is a 53-year-old man with ANCA-associated vasculitis who, after starting enoxaparin for deep vein thrombosis, experienced worsening renal function despite improvement in his pulmonary and serological vasculitis markers. A second renal biopsy was crucial to diagnose the superimposed ARN, leading to a change in therapy and renal recovery. The second case is a 73-year-old man with chronic kidney disease who developed an acute kidney injury initially attributed to post-infectious glomerulonephritis. The initiation of prophylactic LMWH was followed by further, severe deterioration of renal function requiring dialysis. In this case as well, a second biopsy revealed the presence of superimposed ARN. The discontinuation of anticoagulant therapy led to the resolution of hematuria and the cessation of dialysis. In both cases, the diagnosis was confirmed by positive Perl's staining and immunohistochemical findings of tubular damage. Conclusions: These cases demonstrate that ARN is not an exclusive complication of oral anticoagulants but can also be induced by LMWH. ARN can mask or overlap with other renal pathologies, making diagnosis difficult. Renal biopsy, sometimes repeated, remains the gold standard for an accurate differential diagnosis. This makes it possible to avoid inappropriate therapy escalation and to guide correct clinical management. Greater awareness of this clinical entity is necessary in all anticoagulated patients who develop acute kidney injury.