An 8-year-old boy presented with a painful crusted lesion over the left forearm. Cutaneous examination revealed a solitary coin-sized, indurated, ulcerated, tender plaque with central brownish adherent crust and yellowish-brown dried exudates at the margin (Fig. 1). There was no preceding history of any insect or arthropod bite. The Gram stain from pus obtained from underneath the crust revealed gram-positive cocci, and culture grew both Group A b-hemolytic streptococci and Staphylococcus aureus. A diagnosis of ecthyma was made; oral cefixime and topical mupirocin ointment were prescribed along with removal of crust using diluted white vinegar soaks. Complete healing with scarring occurred within 2 weeks.

Fig. 1 Solitary ulcer with central adherent crust and yellowish-brown dried up exudates at the ulcer’s margin.

Ecthyma denotes cutaneous bacterial infection that extends deep into the dermis and heals with scarring. It usually develops over disrupted skin on extremities and rapidly develops into a vesicopustule and finally a hemorrhagic crust. Differential diagnoses include arthropod bites, leishmaniasis, ecthyma gangrenosum (vide infra), pyoderma gangrenosum, Mycobacterium marinum infection, and papulonecrotic tuberculid. Two related terms need to be differentiated from ecthyma: Ecthyma gangrenosum (a gangrenous ulcer with a central eschar surrounded by an erythematous halo) a pseudomonal infection that occurs in immuno-suppressed or gravely ill patients, and Ecthyma contagiosum (solitary pustular lesions on hands) resulting from the direct contact of damaged skin with animal infected by a virus of Parapoxvirus group.