Differential Diagnosis for AKI with Eosinophiluria in the Context of MRSA Infective Endocarditis

Single Most Likely Diagnosis

• Acute Interstitial Nephritis (AIN): This is a common cause of AKI, especially in the context of infections and medications. Eosinophiluria is a hallmark of AIN, and MRSA infective endocarditis could be the precipitating factor, possibly through the use of antibiotics or the immune response to the infection itself.

Other Likely Diagnoses

• Immune Complex Mediated Glomerulonephritis: This condition can occur in the setting of chronic infections, including endocarditis. The immune complexes formed in response to the infection can deposit in the kidneys, leading to inflammation and AKI.
• Severe Sepsis or Septic Shock: MRSA infective endocarditis can lead to severe sepsis or septic shock, which is a well-known cause of AKI. While eosinophiluria is not a typical finding, the severity of the infection could lead to a complex presentation.
• Medication-Induced Nephrotoxicity: Patients with MRSA infective endocarditis are often treated with nephrotoxic antibiotics. Eosinophiluria could be seen in the context of an allergic interstitial nephritis, but other forms of nephrotoxicity (e.g., direct tubular injury) are also possible.

Do Not Miss Diagnoses

• Antibody-Mediated Rejection (if patient has a history of kidney transplant): Although less common, in patients with a history of kidney transplantation, antibody-mediated rejection should be considered, especially if there are signs of an immune response.
• Thrombotic Microangiopathy (TMA): This condition, which includes thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS), can present with AKI and is associated with a high mortality rate if not promptly recognized and treated.

Rare Diagnoses

• Eosinophilic Granulomatosis with Polyangiitis (Churg-Strauss Syndrome): A rare autoimmune condition characterized by asthma, eosinophilia, and vasculitis affecting multiple organ systems, including the kidneys.
• IgA Nephropathy with Eosinophiluria: While IgA nephropathy is a common cause of kidney disease, the presence of eosinophiluria is unusual and might suggest an atypical presentation or a secondary form of IgA nephropathy.