Prosthetic valve endocarditis from Mycobacterium chimaera infection causing granulomatous interstitial nephritis

Area of Science:

• Infectious Diseases
• Nephrology
• Cardiology

Background:

• Mycobacterium chimaera is a rare pathogen implicated in prosthetic valve endocarditis, often following cardiopulmonary bypass.
• Granulomatous interstitial nephritis is an uncommon renal manifestation of infectious diseases.

Observation:

• A 63-year-old female with a prosthetic aortic valve presented with constitutional symptoms and worsening renal function.
• Initial investigations, including fat pad aspirate and bone marrow biopsy, were inconclusive for specific etiology.
• Transesophageal echocardiogram revealed aortic root abscess and valve vegetation, while renal biopsy showed granulomatous interstitial nephritis.

Findings:

• Despite negative acid-fast bacilli (AFB) stains on initial biopsies, blood cultures eventually identified Mycobacterium chimaera.
• Treatment with prednisone initially improved renal function, but antimicrobial therapy was initiated upon pathogen identification.
• The patient showed significant renal function improvement and resolution of cardiac lesions after three-drug antimicrobial treatment.

Implications:

• This case underscores the importance of considering Mycobacterium chimaera in patients with prosthetic valve endocarditis and unexplained renal dysfunction.
• It highlights that granulomatous interstitial nephritis can be a manifestation of M. chimaera infection, even with negative AFB stains.
• Prompt diagnosis and appropriate antimicrobial treatment are essential for favorable outcomes in these complex cases.