(ek-thi´mah) A shallowly ulcerative form of impetigo, chiefly on the shins or forearms. Skin infection usually caused by neglect of impetigo. Has shallow lesions with crusts or scabs, followed by discoloration and scarring. Streptococcus pyogenes and/or Staphylococcus aureus are the bacteria responsible for ecthyma.
Contagious ecthyma (contagious pustular dermatitis) is caused by orf virus, a poxvirus that infects ruminants (most often sheep and goats). Farmers, veterinarians, zoo caretakers, and others with direct animal contact are at risk. The cutaneous findings pass through 6 stages that last about 1 wk: (1) papular, a single red edematous papule appears on a finger (most commonly right index finder); (2) target, a larger nodule with a red center surrounded by a white ring with a red periphery; (3) acute, a rapidly growing infected-looking tumor; (4) regenerative, a nodule with black dots covered with a thin transparent crust; (5) papillomatous, a nodule with a surface studded with small projections; (6) regressive, a nodule flattened with a thick crust. Patients can develop regional adenopathy, lymphangitis, and fever.
Ecthyma gangrenosum (EG) is a well-recognized cutaneous infection most commonly associated with a Pseudomonas aeruginosa bacteremia. EG usually occurs in patients who are critically ill and immunocompromised. The characteristic lesions of EG are hemorrhagic pustules or infracted-appearing areas with surrounding erythema that evolve into necrotic ulcers surrounded by erythema. These were first described in association with Pseudomonas septicemia by Barker in 1897 and were later given the name “ecthyma gangrenosum” by Hitschmann and Kreibich.
See also: * Infections Associated with Lymphedema