Crust is gray-yellow and is thicker and harder than the crust of impetigo. A shallow punched-out ulceration is apparent when adherent crust is removed. Deep dermal ulcer has a raised and indurated surrounding margin. Ecthyma heals slowly and commonly produces a scar. Regional lymphadenopathy often is seen, even with solitary lesions.
Important factors contribute to the development of streptococcal pyodermas or ecthyma.
Poor hygiene Untreated impetigo that progresses to ecthyma most frequently occurs in patients with poor hygiene. Prior GAS infection can be detected by anti-DNase beta. Ecthyma lesions show dermal necrosis and inflammation. A deep and superficial granulomatous perivascular infiltrate occurs along with endothelial edema. Heavy crust covers the surface of the ecthyma ulcer.