A 68-year-old man presents to your urgent care with 5 days of worsening rash, fever, malaise, and facial swelling. He reports that the rash began on his upper trunk and has spread to involve his face, arms, and legs. Examination shows a diffuse morbilliform eruption involving the face, trunk, and extremities (approximately 60% body surface area), with periorbital edema, cervical lymphadenopathy, and mild hand swelling. He denies skin pain, blistering, and mouth sores, but he reports decreased appetite and dark urine.
His vital signs are: temperature, 102.1°F; heart rate, 108 beats/min; blood pressure, 132/78 mm Hg; respiratory rate, 18 breaths/min; and SpO₂,97% on room air. In taking a thorough medication history, you learn that his current medications include:
- Lisinopril: 20 mg daily, for the past 8 years
- Atorvastatin 40 mg nightly, for the past 5 years
- Metformin 1000 mg twice daily, for the past 10 years
- Allopurinol 100 mg daily, started 6 weeks ago for gout
- Aspirin 81 mg daily, for the past 6 years
What medication is the most likely culprit?
- Aspirin
- Metformin
- Allopurinol
- Atorvastatin
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Correct answer: c. Allopurinol
Rationale: Allopurinol is one of the most common causes of drug-induced hypersensitivity syndrome (DIHS). The timing is classic, as DIHS typically develops 2 to 8 weeks after initiation of the culprit medication. Chronic medications that have been tolerated for years are much less likely to be responsible.
The allopurinol was stopped immediately. The presence of fever, facial edema, lymphadenopathy, and possible hepatic involvement (report of dark urine) raised concern for a systemic reaction. You obtained a complete blood cell count with differential and a comprehensive metabolic panel to assess for eosinophilia, atypical lymphocytes, hepatitis, kidney injury, and other organ involvement because of his concerning symptoms. Because DIHS severity and disposition depend on laboratory findings and possible internal organ involvement, the patient remained in urgent care until his laboratory results were available. He was eventually referred to the emergency department for further evaluation and management.
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Tracey Davidoff, MD, FACP, FCUCM, has practiced Urgent Care Medicine for more than 15 years. She is Board Certified in Internal Medicine. Dr. Davidoff is a member of the Board of Directors of the Urgent Care Association and serves as Co-Editor-in-Chief of the College of Urgent Care Medicine’s “Urgent Caring” publication. She is also the Vice President of the Southeast Regional Urgent Care Association and a member of the editorial board of the Journal of Urgent Care Medicine. At EB Medicine, Dr Davidoff is Editor-In-Chief of Evidence-Based Urgent Care, and co-host of the Urgentology podcast.
