Micro & Immunology · patient case question
What is the most likely diagnosis of this second presentation?
Patient case: Rash After Local Anesthetic in a Child
Patient: 10-year-old male
Chief Complaint: Restorative treatment on two mandibular molars.
Background: Healthy, no known allergies, no previous dental treatment requiring anesthesia. Immunizations current.
Medications: None
Vital Signs: Baseline: BP 100/62 mmHg · HR 86 bpm · RR 18 · T 98.4°F
Findings: Twenty minutes after administration of 2% lidocaine with 1:100,000 epinephrine, he develops a generalized raised urticarial rash over the trunk and arms, accompanied by nausea, one episode of vomiting, and loose stools. Mild expiratory wheeze is audible. Airway is patent, phonation is normal, and blood pressure remains stable at 98/60 mmHg.
Show answer and explanation
Correct answer: B. Erythema multiforme
- A. Incorrect. Erosive lichen planus presents with bilateral reticular white striae and erosions, follows a chronic waxing and waning course, and does not cause target lesions on the skin.
- B. Correct. Symmetric target or iris lesions on the extremities with hemorrhagic, crusted lips are the defining presentation of erythema multiforme. It is most often triggered by herpes simplex virus or by medications, and it characteristically affects young patients with abrupt onset.
- C. Incorrect. Primary herpetic gingivostomatitis affects young children with fever, malaise, and fiery erythematous gingivitis with vesicles throughout the mouth. Skin target lesions are not part of it.
- D. Incorrect. Pemphigus vulgaris produces flaccid intraoral bullae with a positive Nikolsky sign, affects patients typically in their fifth and sixth decades, and does not produce target lesions.
Note: Recognize the spectrum: erythema multiforme minor involves one mucosal site with limited skin lesions. Stevens-Johnson syndrome and toxic epidermal necrolysis represent the severe end, defined by the percentage of body surface area detached, and both are medical emergencies.
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