Erysipelas - St. Anthony's Fire

Woman with itchy arm
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Erysipelas is a superficial infection of the skin, which typically involves the lymphatic system. Erysipelas is also known as St. Anthony's Fire, an accurate description of the intensity of this rash. Erysipelas was a feared disease in pre-antibiotic days, especially in infants.

Cause of Erysipelas

Erysipelas is most often caused by a specific Streptococcus bacteria known as Group A Streptococcus. In a few cases, it can be caused by other types of Streptococcus or Staphylococcus bacteria.

Some cases of erysipelas have an inciting wound such as trauma, an abrasion, or some other break in the skin that precede the fiery infection. However, in most cases, no break in the skin can be found.

Appearance of Erysipelas

Erysipelas was previously found mainly on the face. However, now it is seen most commonly on the lower extremities. Erysipelas tends to occur in areas where the lymphatic system is obstructed. A cluster of symptoms typically precede the appearance of the rash by 4 to 48 hours. These symptoms include fever, chills, fatigue, anorexia, and vomiting. The rash then quickly appears as a bright red, hot, swollen, shiny patch that has clearly defined borders. The consistency of the rash is similar to an orange peel, also known as "peau d'orange".

  • Picture of erysipelas on the cheek
  • Picture of erysipelas on the face

Diagnosis of Erysipelas

Erysipelas is diagnosed mainly by the appearance of the rash.

Blood tests and skin biopsies generally do not help make the diagnosis. In the past, saline solution was injected into the edge of the rash, aspirated back out, and cultured for bacteria. This method of diagnosis is not used anymore because bacteria were not found in the majority of cases. If the preceding symptoms such as fever and fatigue are significant enough, sometimes blood is drawn and cultured for bacteria to rule out sepsis.

Treatment of Erysipelas

Erysipelas is treated with antibiotics. A variety of antibiotics can be used including penicillin, dicloxacillin, cephalosporins, clindamycin, and erythromycin. Most cases of erysipelas can be treated with oral antibiotics. However, cases of sepsis, or infections that do not improve with oral antibiotics require IV antibiotics administered in the hospital.

Recurrence of Erysipelas

Even after appropriate treatment with antibiotics, erysipelas can recur in 18% to 30% of cases. People who are susceptible to recurrence are those with compromised immune systems or compromised lymphatic systems. Because erysipelas can damage the lymphatic system, the infection itself can be a setup for recurrence. Some people with recurrent infections must be treated daily with low-dose antibiotics as a prevention of further infections.

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