A patch test confirmed phenobarbital-induced fixed drug eruption in a child

Area of Science:

• Dermatology
• Pharmacology

Background:

• Fixed drug eruption (FDE) is an adverse drug reaction characterized by recurrent, well-demarcated lesions at the same site(s) upon re-exposure to the causative agent.
• Pediatric cases of FDE are less common, and identifying the specific drug trigger can be challenging.

Observation:

• A 10-year-old girl presented with multiple hyperpigmented plaques following treatment with acetylsalicylic acid and phenobarbital suppositories.
• The patient developed pruritic red plaques on her thigh 12 hours after drug intake.
• Patch testing revealed a positive reaction to phenobarbital on residual pigmented lesions, while acetylsalicylic acid and other anticonvulsants tested negative.

Findings:

• Phenobarbital was identified as the causative agent of fixed drug eruption in this pediatric case.
• The patch test was crucial in differentiating between phenobarbital and acetylsalicylic acid as the trigger.
• This case adds to the limited literature on phenobarbital-induced FDE in children.

Implications:

• Accurate drug-induced eruption diagnosis is vital for patient management and preventing future reactions.
• Patch testing is a valuable diagnostic tool for identifying specific drug triggers in FDE.
• Increased awareness of phenobarbital as a potential cause of FDE in pediatric populations is warranted.