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Kidney Week

Abstract: TH-PO670

Atypical Hemolytic Uremic Syndrome with Normal Complement Studies in a Patient with Complement Factor I Deficiency

Session Information

Category: Glomerular Diseases

  • 1402 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Monk, Brian, The University of Mississippi Medical Center, Jackson, Mississippi, United States
  • Foster, Danielle C., The University of Mississippi Medical Center, Jackson, Mississippi, United States
  • Atari, Mohammad, The University of Mississippi Medical Center, Jackson, Mississippi, United States
  • Hassanein, Mohamed, The University of Mississippi Medical Center, Jackson, Mississippi, United States
Introduction

Atypical hemolytic uremic syndrome (AHUS) is a type of thrombotic microangiopathy (TMA) that presents with organ dysfunction, particularly involving the kidney. AHUS occurs due to dysfunction in the alternative complement pathway and occurs sporadically, secondary to malignancy, drugs, or autoimmune diseases, or can be inherited. We present a rare case of AHUS due to a genetic mutation in complement factor I (CFI) and normal complement studies.

Case Description

A 27-year-old female with uncontrolled hypertension (HTN) was admitted for hypertensive emergency (blood pressure 211/119) and acute kidney injury (Cr 15.4 mg/dL, baseline 3 mg/ dL). Further workup showed hemoglobin 8.2 g/dL (ref: 11.2-15.7 g/dL), platelets 78 K/uL (ref: 182-369 K/uL), low haptoglobin, and elevated LDH. Infectious and autoimmune processes were ruled out. Compliment levels C3 and C4 were normal. While awaiting an AHUS complement panel, she required dialysis and underwent a kidney biopsy which showed TMA with 40% interstitial fibrosis and 60% acute tubular injury. Eculizumab therapy was initiated for suspicion of AHUS based on biopsy findings. A few days later, AHUS panel came back showing no abnormalities in the alternative complement pathway, except elevated C5b-9. After discharge, she was found to have a heterozygous mutation of the CFI gene which has been associated with autosomal dominant AHUS. Eculizumab therapy was continued and the patient was monitored closely outpatient.

Discussion

In the setting of normal complement studies, one cannot rule out AHUS as the primary cause of TMA. If the index of suspicion is high, it is recommended to start empirical Eculizumab and send off genetic studies to rule out a genetic cause of the AHUS, which may prevent unnecessary cessation or delay in Eculizumab therapy, and hence improve outcomes.