The biopsy specimen revealed pseudoepitheliomatous hyperplasia and a neutrophil-predominant dermal inflammatory infiltrate with microabscesses in the dermis and epidermis. Stains were negative for bacteria and fungi. Cultures of the punch biopsy specimen yielded methicillin-resistant Staphylococcus aureus. Tissue cultures were negative for mycobacterial and fungal organisms.
Oral cephalexin was administered. The plaques were covered with nonadherent sterile dressings. Within 2 days, the pustules had resolved and the erythema, exudation, and pain had diminished. Cephalexin therapy was continued in view of the excellent therapeutic response despite antimicrobial sensitivities showing resistance. Within 3 weeks, only mild erythema with slight scaling remained.
Pustule-Studded Plaques After Abrasion Injury—Diagnosis. Arch Dermatol. 2006;142(12):1643-1648. doi:10.1001/archderm.142.12.1644-a