Differential Diagnosis
The patient's symptoms of rash, fevers, hematuria, and proteinuria following a course of oral penicillin for a UTI suggest an immune-mediated or allergic reaction. Here's a categorized differential diagnosis:
Single most likely diagnosis
- C. Acute interstitial nephritis (AIN): This condition is often caused by an allergic reaction to medications, including antibiotics like penicillin. The timing of the symptoms (10 days after completing the antibiotic course) and the combination of rash, fever, hematuria, and proteinuria are consistent with AIN.
Other Likely diagnoses
- B. Crescentic glomerulonephritis: Although less common, this condition can be triggered by infections or immune complex deposition and could explain the hematuria and proteinuria. However, the presence of a rash and the temporal relationship to antibiotic use make it less likely than AIN.
- A. Acute renal tubular necrosis: This condition is more commonly associated with ischemia or nephrotoxicity (e.g., from certain medications or contrast agents) rather than an allergic reaction to penicillin. The clinical presentation could fit, but it's less directly linked to the recent antibiotic use.
Do Not Miss
- D. Pyelonephritis: Although the patient was recently treated for a UTI, recurrence or inadequate treatment could lead to pyelonephritis, which would present with fever and potentially hematuria. The rash would be an unusual feature but could be part of a systemic response. Missing this diagnosis could lead to severe consequences, including sepsis.
- Systemic vasculitis: Conditions like ANCA-associated vasculitis could present with similar symptoms, including renal involvement and rash. While less likely, missing this diagnosis could have significant implications for treatment and prognosis.
Rare diagnoses
- Goodpasture's syndrome: An autoimmune disease that could explain the renal symptoms but would typically be associated with anti-GBM antibodies and is much less common.
- Other autoimmune diseases: Conditions like lupus nephritis or IgA nephropathy could present with similar renal symptoms but would typically have other systemic features and are less directly linked to recent antibiotic use.