Ecthyma is an ulcerative bacterial skin infection caused by group A beta-hemolytic streptococci and often secondarily associated with staphylococci. As ecthyma often begins superficially and extends into the dermis, it is often referred to as a deeper form of impetigo. Unlike impetigo, which only affects the stratum corneum, ecthyma extends into the dermis and results in a scar.

Clinically, the lesions of ecthyma appear as vesicles or pustules that ulcerate and crust over. The lower extremities are sites of predilection.

Immunosuppression, poor hygiene, overcrowding, malnutrition, humidity, and pre-existing trauma to the tissues all predispose one to infection. It has also been seen on the lower legs of military trainees in tropical climates. It is more common at the extremes of age.