Erysipelas

Erysipelas is one of the most common skin infections resulting in hospitalization. With respect to the terminology, the term erysipelas is differentiated from cellulitis [1]. The term cellulitis may be a source of confusion because it groups several entities together [2].

Erysipelas is considered to be a specific type of cellulitis or acute bacterial dermohypodermitis. It is characterized by superficial inflammation of the skin including the superficial lymphatic system and is most commonly caused by beta-hemolytic streptococci (usually group A). Clinical features consist of an inflammatory patch with clearly defined borders with surrounding healthy skin. Cellulitis, on the other hand, is a bacterial dermohypodermitis involving the deep dermis and subcutaneous tissue. It is usually caused by Streptotoccus bacteria but other microorganisms (particularly Staphylococcus aureus) have also been implicated. Clinically, the inflammatory patch is much less sharply demarcated from surrounding healthy skin.

Typical erysipelas is caused by beta-hemolytic streptococcus, usually group A, but also other groups, particularly group G (22% group G in a Finnish study) [3]. Staphyloccus aureus does not play a pathogenic role in typical erysipelas but can cause other forms of bacterial dermohypodermitis, especially those associated with boils and/or abscesses [4].

Erysipelas most commonly occurs on the lower extremities and much more rarely on the upper extremities, face and trunk [4].

Bacterial inoculation into a break in the skin is the cause of the infection. Typical erysipelas is due to bacterial toxins with a low bacterial density within the lesions. It probably results from an immunologic hypersensitivity reaction to streptococcal antigens, which leads to inflammation (local production of IL-1 and TNF) and rapid elimination of the bacteria.