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Kidney Week

Abstract: FR-PO704

Mycobacterium Chimaera: An Unusual Cause of Hypercalcemia and Kidney Injury

Session Information

Category: Trainee Case Report

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Sawaf, Hanny, Trihealth, Cincinnati, Ohio, United States
  • Nakhoul, Georges, Cleveland Clinic Foundation, Cleveland, Ohio, United States
  • Mehdi, Ali, Cleveland Clinic, Mayfield Hts, Ohio, United States
Introduction

Mycobacterium Chimaera is an indolent nontuberculous mycobacterium that has been recently associated with outbreaks of prosthetic valve endocarditis throughout Europe and the United States. Contaminated heater-cooler devices in the cardiothoracic operating rooms have been implicated as the cause of the outbreak. Hypercalcemia and kidney involvement have rarely been reported as part of the disease presentation. We hereby present a case of M. Chimaera prosthetic valve endocarditis presenting with hypercalcemia and kidney dysfunction.

Case Description

A 63-year-old male with a history of bicuspid aortic valve status post bioprosthetic AVR presented with generalized weakness, fatigue, and altered sensorium. MRI of the brain revealed small embolic events that prompted a TEE which was suspicious for vegetations on the bioprosthetic valve along with valve dehiscence and perivalvular abscess. He was thus transferred to our facility for evaluation of re-do surgery. On evaluation, he was found to have an AKI with a creatinine of 1.7 mg/dl (baseline around 1). He was also notably hypercalcemic at 12 mg/dl with an undetectable PTHrP level. Creatinine and calcium trended down slowly with hydration and the patient was eventually taken to the OR for AVR. While 25-OH vitamin D level was low (20.8 ng/ml), the 1,25-OH vitamin D level was elevated at 65.4 pg/ml. Microbiologic evaluation of the explanted valve revealed moderate acid-fast bacilli by Ziehl-Neelson stain and the cultures were positive for Mycobacterium Chimaera. The patient was also found to have multifocal choroiditis on ophthalmic evaluation, which was indicative of disseminated mycobacterial infection. He was thus treated with a prolonged course of rifampin, ethambutol, and azithromycin.
The patient was eventually discharged home in good condition with complete normalization of creatinine and calcium levels.

Discussion

Mycobacteria are associated with elevated 1,25-OH Vitamin D levels due to production of 1-alpha-hydroxylase enzyme by activated macrophages. The ensuing hypercalcemia can certainly lead to kidney dysfunction but M. Chimaera has also been associated with granulomatous interstitial nephritis. Treatment focuses on antibiotic therapy and in the case of prosthetic valve endocarditis, surgical treatment whenever possible.