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Kidney Week

Abstract: FR-PO200

Amoxicillin-Induced Crystalline Nephropathy

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Mousseaux, Cyril, Assistance Publique - Hopitaux de Paris, Paris, Île-de-France, France
  • Tang, Ellie, INSERM, Paris, Île-de-France, France
  • Tristant, Maxime, Assistance Publique - Hopitaux de Paris, Paris, Île-de-France, France
  • Mesnard, Laurent, Assistance Publique - Hopitaux de Paris, Paris, Île-de-France, France
  • Luque, Yosu, Assistance Publique - Hopitaux de Paris, Paris, Île-de-France, France
  • Rafat, Cedric, Assistance Publique - Hopitaux de Paris, Paris, Île-de-France, France
  • Buob, David, Assistance Publique - Hopitaux de Paris, Paris, Île-de-France, France
  • Letavernier, Emmanuel, Assistance Publique - Hopitaux de Paris, Paris, Île-de-France, France
Introduction

Amoxicillin-induced crystalline nephropathy (AICN) is characterized by the sudden onset of acute kidney injury (AKI) and microscopic examination of the urine revealing characteristic birefringent needles under polarized light. Surprisingly, the presence of intratubular amoxicillin crystals is not reported. We report here the first case of intrarenal deposits of amoxicillin crystals.

Case Description

A 55-year-old woman was referred for AKI within one week of the initiation of amoxicillin antibiotic therapy for mitral endocarditis. She was euvolemic and had no fever, tachycardia, or rash. Urine analysis revealed no signs of leukocyturia or hematuria. The initial serum creatinine level was 5.42 mg/dL and the urine protein/creatinine ratio was 1 g/g. Complement and serum electrophoresis results were within normal range. Renal ultrasound was unremarkable. Urine microscopy after amoxicillin withdrawal did not reveal any crystals.
Renal biopsy detected elongated optically empty formations within the tubular lumen, suggesting the presence of material dissolved during sample preparation. Further examination of the frozen fragment of the kidney biopsy specimen under polarized light revealed numerous intratubular birefringent structures. Scanning electron microscopy confirmed the presence of crystals within the tubular lumen, suggesting amoxicillin crystallization. The definitive proof that these crystals were composed of amoxicillin was obtained through attenuated total reflectance (ATR)Fourier-transform infrared spectroscopic analysis of frozen kidney biopsy sections.

Discussion

Despite being one of the most frequent crystalline nephropathies, the presence of intratubular crystals of amoxicillin in situ has yet to be documented.
This case highlights several important messages. First, the processing of kidney biopsies can cause dissolution of crystals, emphasizing the need for systematic analysis of frozen tissue under polarized light in suspected cases of crystalline nephropathy. Second, infrared spectroscopic analysis plays a crucial role in identifying the causative substance. Finally, the presence of crystals in urine is transient and crystalluria analyses may be negative if not performed during exposure to amoxicillin.