**Core Concept**
The patient's presentation of acute kidney injury (indicated by elevated serum creatinine and blood urea nitrogen levels) with proteinuria, hematuria, and the presence of eosinophils in the urine suggests an immune-mediated glomerulonephritis, likely IgA nephropathy or post-infectious glomerulonephritis (PIGN), but the presence of eosinophils makes IgA nephropathy less likely.

**Why the Correct Answer is Right**
The patient's symptoms of fever, rash, and malaise followed by the development of renal dysfunction suggest an immune-mediated response to an infection. The presence of eosinophils in the urine is indicative of an allergic or immune-mediated response, which is consistent with a diagnosis of allergic interstitial nephritis (AIN). AIN is often precipitated by antibiotics, NSAIDs, or other medications. The patient's recent history of fever and rash may indicate a recent infection, and the subsequent development of renal dysfunction is consistent with AIN.

**Why Each Wrong Option is Incorrect**
**Option A:** While IgA nephropathy can present with hematuria and renal dysfunction, the presence of eosinophils in the urine and the patient's recent history of fever and rash make this diagnosis less likely.
**Option B:** Post-infectious glomerulonephritis typically presents with hematuria and renal dysfunction, but it does not typically involve eosinophils in the urine.
**Option C:** Acute tubular necrosis (ATN) is a common cause of acute kidney injury, but it is not typically associated with the presence of eosinophils in the urine.
**Option D:** Diabetic nephropathy is a common cause of chronic kidney disease, but it is not typically associated with the acute presentation described in this patient.

**Clinical Pearl / High-Yield Fact**
The presence of eosinophils in the urine is a key finding in allergic interstitial nephritis, and it should prompt an investigation into the patient's medication history and recent infections.

**Correct Answer:** C.