A 40-year-old man presented with nausea, fever, and joint pain, and was found to have acute kidney injury. He had recently been treated for H. pylori infection with omeprazole, amoxicillin, and clarithromycin. On examination, he had a rash and lower extremity edema. Urinalysis showed white blood cells and white cell casts. The diagnosis was acute interstitial nephritis, likely caused by a drug reaction to antibiotics and omeprazole, given the presentation of fever, rash and acute kidney injury after starting new medications.

1. QUESTION OF THE WEEK

2. HISTORY
• A 40-year-old man presents to the emergency
department with
• Nausea
• fever,
• and arthralgias..

3. History
• Twelve days ago, he was evaluated by a
physician for epigastric abdominal pain and
was diagnosed with Helicobacter
pylori infection on the basis of a serologic test.

4. History
• He began a 14-day course of omeprazole,
amoxicillin, and clarithromycin, and his
epigastric pain gradually improved.
• The nausea, fever, and arthralgias began 3
days ago.
• He has no cough, diarrhea, or urinary
symptoms

5. On examination
• he has a heart rate of 87 beats per minute, a
blood pressure of 155/90 mm Hg, and a
temperature of 38.0°C.
• The abdomen is nontender.

6. On examination
• He has an erythematous maculopapular rash
over his chest and back
• Trace edema in both lower extremities.

7. Labs
• His serum creatinine level has increased from
0.9 mg/dL 6 months ago to 2.9 mg/dL today
(reference range, 0.8–1.3).
• Other laboratory findings are as follows:

8. LABS
• Leukocyte count (per mm3) 14,000
• Hemoglobin (g/dL) 13
• Platelet count (per mm3) 250,000
• Sodium (mEq/liter) 136
• Potassium (mEq/liter) 5.5
• Chloride (mEq/liter) 101
• Bicarbonate (mEq/liter) 19
• Blood urea nitrogen (mg/dL) 50

9. Urinalysis
• 1+ leukocyte esterase
• negative nitrite
• 1+ protein.
Urine microscopy:
• 1 to 3 red cells per high-power field (reference
range, 0–2),
• 21 to 30 white cells per high-power field (0–2),
• white-cell casts.
• Urine Gram's stain is negative for bacteria.

10. Which one of the following diagnoses is most
likely in this case?
A. Acute interstitial nephritis
B. Immunoglobulin A nephropathy
C. Pyelonephritis
D. Postinfectious glomerulonephritis
E. Acute tubular necrosis

11. The correct answer
• Acute interstitial nephritis

12. Key Learning Point
• In a patient with a fever, rash, and acute
kidney injury after starting a new medication,
the most likely diagnosis is drug-induced
acute interstitial nephritis

13. Acute interstitial nephritis (AIN)
• may be caused by a broad range of disorders
including autoimmune diseases and
infections; however, medications account for
more than 75% of all cases.
• Antibiotics, NSAIDs, and PPIs are relatively
common causes of drug-induced AIN.
• The classic presentation of AIN is fever, rash,
arthralgias, peripheral eosinophilia, and
kidney failure.

14. Pyelonephritis
• can cause fever and pyuria, but urine microscopy is
usually also notable for bacteriuria,
• The Gram stain would be positive
• positive urine culture.
• Pyelonephritis typically also leads to flank pain and
may feature irritative voiding symptoms if there is
associated cystitis.
• In addition, acute pyelonephritis does not cause a
maculopapular rash or a decline in kidney function
unless there is associated effective circulating
volume depletion.

15. Acute tubular necrosis
• is typically characterized by a history of either
exposure to a nephrotoxic agent or ischemic
injury from effective volume depletion.
Furthermore, the urine sediment typically has
granular casts rather than white-cell casts.

16. IgA nephropathy and
postinfectious glomerulonephritis
• are characterized by proteinuria and
hematuria, including red-cell casts.

17. Reference
• NEJM December 20, 2106
•