Ecthyma

# Overview
Ecthyma is an ulcerative pyoderma of the skin caused by bacteria such as Pseudomonas (the most common isolate), Streptococcus pyogenes, and Staphylococcus aureus. Because ecthyma extends into the dermis, it is often referred to as a deeper form of impetigo.

# Ecthyma
- Ecthyma is an ulcerative pyoderma of the skin caused by bacteria such as Pseudomonas (the most common isolate), Streptococcus pyogenes, and Staphylococcus aureus. Because ecthyma extends into the dermis, it is often referred to as a deeper form of impetigo.
- Causes include insect bites and an ignored minor trauma. Wound cultures usually reveal that the lesions are 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 like 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
- Ecthyma 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.

# Etiology
- Ecthyma can be seen in areas of previously sustained tissue injury (e.g., excoriations, insect bites, dermatitis). Ecthyma can be seen 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.

# Pathophysiology
- Ecthyma begins similarly to superficial impetigo. Group A beta-hemolytic streptococci may initiate the lesion or may secondarily infect preexisting wounds. Preexisting 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.
- There is no racial or sexual dominance in Ecthyma.

# Morbidity/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 approximately 1%.

# Treatment

## Antimicrobial Regimen
- Methicillin-Susceptible Staphylococcus Aureus
- Preferred regimen (1): Dicloxacillin 250 mg PO qid for 7 days.
- Preferred regimen (2): Cephalexin 250 mg PO qid for 7 days.
- Methicillin-Resistant Staphylococcus Aureus
- Preferred regimen (1): Doxycycline 100 mg PO bid
- Preferred regimen (2): Clindamycin 600 mg every 8 h IV or 300450 mg PO qid
- Preferred regimen (3): Sulfamethoxazole-trimethoprim 2540 mg/kg/d in 3 divided doses IV or 2530 mg/kg/d in 3 divided doses PO