Cutaneous drug eruptions are a common adverse effect occurring shortly after initiation of a new medication. The morphology of these rashes is commonly described as erythematous macules and papules. We report the case of a 73-year-old male who developed a pruritic macular rash distributed throughout the trunk and extremities three days after being administered subgingival minocycline HCl microspheres following a periodontal procedure. The patient had no recent infections, new medications, or history of tetracycline intolerance. Physical exam revealed erythematous macules and patches, and skin biopsy was consistent with a medication reaction and biopsy findings demonstrated perivascular dermatitis with numerous eosinophils. Given the close temporal relationship, lack of other new medications, and supportive biopsy findings, a drug hypersensitivity reaction was deemed the most probable diagnosis. Clobetasol cream was prescribed, and after approximately seven days, the rash resolved. No recurrence was observed at follow-up. Although systemic minocycline is known to cause hypersensitivity reactions, to our knowledge, there are no previously published reports of cutaneous drug eruptions associated with minocycline HCl microspheres. This case highlights that even local administration has the potential to precipitate clinically significant reactions. Recognition of this potential adverse effect is important for early identification and prevention of unnecessary diagnostic evaluation.
