Ecthyma is an ulcerative pyoderma of the skin, caused by group A beta haemolytic streptococci. As it extends into the dermis, it is often referred to as a deeper form of impetigo.

Epidemiology^1,2

There are no figures for incidence but it is more frequent in children and the elderly.
There is no apparent predilection for race or sex.

Risk factors

• Tissue damage from excoriations, insect bites or dermatitis and a compromised immune system as in diabetes or neutropenia, predisposes to the development of ecthyma. Other causes of immune compromise may include malignancy and HIV.
• Poor hygiene aids spread as does overcrowded living conditions.
• It is more common in hot and humid climates.
• Untreated impetigo with poor hygiene may progress to ecthyma.

Presentation^1,2

Ecthyma begins like impetigo, possibly in a pre-existing wound.

Symptoms

• Ecthyma usually arises on the lower legs or feet of children, diabetics, or neglected elderly people.
• Lesions are typically painful with associated lymphadenopathy.
• In tropical climates, ulcers are commonly found on the ankles and dorsum of the feet.

Signs

• The most commonly affected sites are buttocks, thighs, legs, ankles and feet.
• It starts as a vesicle or pustule over inflamed skin and then deepens to ulcerate with an overlying crust.
• The crust is grey-yellow and is thicker and harder than the crust of impetigo.
• A shallow, punched-out ulcer is seen if the crust is removed.
• The deep dermal ulcer has a raised and indurated margin.
• Ecthyma lesions may remain of constant size and resolve without treatment or they can enlarge to 3 cm in diameter.
• Ecthyma heals slowly, usually with a scar.
• Regional lymphadenopathy is common, even with solitary lesions.

Differential diagnosis^1,2

• Ecthyma gangrenosum (a similar condition caused by pseudomonas). It tends to be more severe and, if diagnosis is delayed, there is a significant mortality.³
• Contagious ecthyma is a term sometimes used for orf.
• Also consider:
  • Insect bites
  • Leishmaniasis
  • Lymphomatoid papulosis
  • Pyoderma gangrenosum
  • Sporotrichosis
  • Venous or arterial ulcers

Investigations^1,2

• Swab for bacteriology
• Check for diabetes (at least urinalysis for glucose and preferably fasting blood glucose).
• FBC for neutropenia.

Associated diseases^1,2

It is more likely to occur in association with diabetes or other conditions of immune compromise.

Management^1,2

Nondrug

• Treatment depends on the progression of the disease.
• Hygiene is important. Use bactericidal soap and frequently change bed linens, towels and clothing.
• Remove crusts and apply an antibiotic ointment daily.
• Povidone-iodine and hydrogen peroxide may be used as antiseptics.

Drugs

• Topical mupirocin ointment is very effective. Fusidic acid and retapamulin are alternatives.⁴ Topical antibiotics are quite satisfactory if the infection is localised.²
• More extensive lesions require oral antibiotics, possibly for several weeks to obtain full resolution.
• Penicillin should be adequate to treat streptococci.
• If S. aureus is also present, an antibiotic resistant to penicillinase may be advised.⁵
• Consider parenteral antibiotics if there is widespread involvement.

Surgical

Gently debride the crusts.

Complications¹

• Ecthyma rarely produces systemic symptoms.
• Invasive complications of streptococcal skin infections include cellulitis, erysipelas, gangrene, lymphangitis, suppurative lymphadenitis and bacteraemia.
• Nonsuppurative complications of streptococcal skin infections include scarlet fever and acute glomerulonephritis. Antibiotics do not appear to reduce the rate of post-streptococcal glomerulonephritis.
• Possible sequelae of secondary untreated S. aureus pyodermas include cellulitis, lymphangitis, bacteraemia, osteomyelitis and acute infective endocarditis. Some S. aureus strains produce exotoxins that can lead to staphylococcal scalded skin syndrome⁶ and toxic shock syndrome.

Prognosis¹

Healing is slow with scar formation but response to appropriate antibiotics occurs over several weeks.

Prevention¹

In tropical climates, pay attention to hygiene and use insect repellents to reduce bites.

Document references

1. Davis L; Ecthyma, Medscape, Nov 2009
2. Ecthyma, Dermnet NZ
3. Yassaee M et al; Ecthyma Gangrenosum, Medscape, Jul 2008
4. Dhar D; Impetigo and Ecthyma, Merck Manuals, 2007
5. Palit A, Inamadar AC; Current concepts in the management of bacterial skin infections in children. Indian J Dermatol Venereol Leprol. 2010 Sep-Oct;76(5):476-88. [abstract]
6. King RW et al; Staphylococcal Scalded Skin Syndrome, Medscape, May 2010

Acknowledgements