|Classification and external resources|
|ICD-10||L08.3 (ILDS L08.830)|
Ecthyma is an ulcerative pyoderma of the skin caused by bacteria such as Pseudomonas (the most common isolate), Streptococcus pyogenes, and Staphylococcus aureus. Ecthyma in humans may also be caused by orf, a zoonotic parapox virus from direct contact with infected sheep and goats. Because ecthyma extends into the dermis, it is often referred to as a deeper form of impetigo. Wound cultures usually reveal the lesions to be teeming with bacteria.
Ecthyma describes ulcers forming under a crusted surface infection. The site may have been that of an insect bite or of neglected minor trauma. It is treated by antibiotics such as cloxacillin, erythromycin, and cephalexin. Pseudomonas infections are often treated with two antibiotics due to frequent resistance.
Ecthyma has a predilection for children and elderly individuals. Outbreaks have also been reported in young military trainees. It usually arises on the lower extremities of children, persons with diabetes, and neglected elderly patients. During wartime in tropical climates, ecthymatous ulcers are commonly found on the ankles and dorsa of the feet.
Ecthyma can be seen in areas of previously sustained tissue injury (e.g., excoriations, insect bites, dermatitis), and in patients who are immunocompromised (e.g., diabetes, neutropenia, HIV infection). Important factors contribute to the development of streptococcal pyodermas or ecthyma: ♦ High temperature and humidity ♦ Crowded living conditions ♦ Poor hygiene
Untreated impetigo that progresses to ecthyma most frequently occurs in patients with poor hygiene. Some strains of Streptococcus pyogenes have a high affinity for both pharyngeal mucosa and skin. Pharyngeal colonization of S. pyogenes has been documented in patients with ecthyma.
Ecthyma begins similarly to superficial impetigo. Group A beta-hemolytic streptococci may initiate the lesion or may secondarily infect pre-existing wounds. Pre-existing tissue damage (e.g., excoriations, insect bites, dermatitis) and immunocompromised states (e.g., diabetes, neutropenia) predispose patients to the development of ecthyma. Spread of skin streptococci is augmented by crowding and poor hygiene.
The difference between ecthyma and impetigo is that in impetigo the erosion is at the stratum corneum, while in ecthyma the ulcer is full thickness and thus heals with scarring. No racial or sexual dominance is seen in ecthyma.
Morbidity and mortality
Ecthyma rarely leads to systemic symptoms or bacteremia. Lesions are painful and can have associated lymphadenopathy. Secondary lymphangitis and cellulitis can occur. Ecthyma does heal with scarring. The rate of poststreptococcal glomerulonephritis is around 1%.