Kidney Week

Abstract: FR-PO0429

Pigment Nephropathy from Hemolysis in Immune Thrombocytopenia (ITP) Mimicking Thrombotic Microangiopathy (TMA): The Value of Kidney Biopsy amid Confounded Serologies

Session Information

• AKI: Case Reports - TMA, Vasculitis, Immune-Mediated Injury, and Systemic Disease
  October 23, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 102 AKI: Clinical, Outcomes, and Trials

Authors

• Mathews, Hella Fiona, Northwell Health, New Hyde Park, New York, United States

Hella Fiona Mathews, MD

• Wanchoo, Rimda, Northwell Health, New Hyde Park, New York, United States

Rimda Wanchoo, MD

• Kim, Sungsoo, Northwell Health, New Hyde Park, New York, United States

Sungsoo Kim, MD

• Wu, Ming, Northwell Health, New Hyde Park, New York, United States

Ming Wu, MD

Introduction

AKI with concurrent thrombocytopenia and anemia often prompts concern for TMA, particularly TTP or aHUS. However, severe intravascular hemolysis can cause heme pigment–induced acute tubular injury (ATI) that clinically mimics TMA. Diagnostic accuracy may be further complicated by distorted serological testing secondary to immunomodulatory therapies

Case Description

A 30-year-old man with known ITP presented with severe thrombocytopenia (platelets 1,000/µL) and was treated with dexamethasone 40mg daily and IVIG 90g daily for 4 days, achieving a transient platelet rise to 70,000/µL. A few days later, his platelets fell to 14,000/µL with a concurrent drop in hemoglobin to 5.9 g/dL. Serum creatinine (baseline normal) peaked to 3.44 mg/dL. Laboratory data were consistent with hemolysis (elevated LDH, low haptoglobin, total bilirubin 3.9 mg/dL). Urinalysis showed blood+, protein+, UPCR 0.8g/g. Given concern for TTP, the patient received one emergent PLEX, then stopped when peripheral smear showed no schistocytes and ADAMTS13 activity returned normal. Complement testing showed elevated soluble C5b-9 and low C4; an aHUS genetic panel was equivocal. dsDNA was transiently positive (15 IU/mL) and later negative; lupus anticoagulant and direct Coombs were positive. PNH flow cytometry and urine hemosiderin were negative. Connective tissue disease was deemed unlikely, as IVIG and plasma exchange likely confounded serologies. Kidney biopsy demonstrated ATI with heme pigment casts and no evidence of TMA. Immunohistochemistry was positive for heme pigment (myoglobin stain positive), consistent with pigment nephropathy in the setting of hemoglobinuria. Supportive care with intravenous fluids was initiated, and the patient continued a prednisone taper for ITP relapse. Serum creatinine improved to 1.76 mg/dL; platelets recovered to within normal limits and anemia improved.

Discussion

This case highlights hemoglobinuric pigment nephropathy as a cause of AKI in the setting of severe hemolysis from ITP that clinically mimicked TMA. The absence of schistocytes and a normal ADAMTS13 activity substantially lowered the probability of TTP, while equivocal complement and autoimmune serologies were likely distorted by IVIG/PLEX and ongoing hemolysis. Kidney biopsy was decisive, preventing unnecessary continuation of plasma exchange or initiation of complement blockade and directing supportive management.