Erysipelas
Key Points
Erysipelas is a nonnecrotizing bacterial infection of the superficial layers of the skin
The most common causative organism is Streptococcus pyogenes (group A streptococci)
S. pyogenes has a special predilection to invade the dermal lymphatics
The main presenting symptoms are tenderness, pain, fever, and malaise
A history of a scratch or an insect bite may be elicited from the patient
The affected skin shows a bright red, well-defined inflamed area with a raised edge, ± bullae on the border of the lesion
Isolated eyelid involvement is extremely rare
Erysipelas is generally considered a nonculturable condition, and attempts to culture bacteria are usually unsuccessful
Radiology is of no particular value in the diagnostic workup of the disease
The condition should be differentiated from allergic contact dermatitis and necrotizing fasciitis
Empiric antimicrobial therapy (β-lactams) should be started immediately
If properly treated, the condition settles within a week or 2, but if it is inadequately treated, it can progress to necrotizing fasciitis
Erysipelas (St. Anthony’s fire) is an acute, nonnecrotizing diffuse bacterial infection of the superficial dermis, upper subcutaneous tissue, and lymphatics, which is hallmarked by the presence of a bright red, well-defined inflamed area of the skin that resembles a rash.1,2,3,4,5,6,7,8,9,10 Traditionally, the special predilection of this disease to involve the superficial dermis was used as a differentiating point to distinguish erysipelas from cellulitis. According to the classic definition of cellulitis, it should involve deeper tissue planes than erysipelas1,2,3,4,5,6,7,8,9,10; however, the current trend in the dermatology literature is to deal with both entities as a single disease rather than two distinct entities. According to this updated view, the definition of cellulitis should be expanded to include both superficial infections (erysipelas) and deeper tissue involvement (cellulitis).1,4,9 This view is supported by the fact that the risk factors, diagnosis, and management of erysipelas are similar to those of cellulitis. In addition, the bacteriology of both conditions is similar, as streptococcal antigens are demonstrated in the dermis and subcutis in both conditions.4 However, both entities will be described separately in this textbook, simply because the term “cellulitis” has special connotations in ophthalmic and oculoplastic literature, which brings to mind specific preseptal and orbital infectious conditions.
Etiology and Pathogenesis
Erysipelas is bacterial in origin and the most common causative organism is Streptococcus pyogenes (group A streptococci, GAS). Other organisms that are less frequently implicated in the pathogenesis of erysipelas include groups B, C, D, G, and F streptococci.1,2,4,10 Staphylococcus aureus may rarely be isolated together with streptococcal species, but it is rarely cultured alone in erysipelas patients, and its isolation should be regarded as an occasional finding.2
In immunologically competent patients, erysipelas usually results from the disruption of the cutaneous barrier.11 A small break in the skin due to an insect bite, a minor scratch, or rarely laser resurfacing allows the organism to gain access to the dermis.4,6,12 As a species, S. pyogenes has a special predilection to invade the dermal lymphatics, whereby they can reach the lymph nodes and later the circulation.13 The mechanism underlying this lymphatic tropism is unknown, but it is hypothesized that the hyaluronan capsule of GAS plays a crucial determinant role.13 This lymphatic affinity is probably why streptococcal life-threatening infections may be observed, even in healthy individuals.
Clinical Presentation
Erysipelas has a special predilection for the lower extremities (70%-90%), upper extremities (12%), and to a lesser extent the face (2%-10%).5,6,7,8 Isolated eyelid erysipelas is extremely rare, and when it is observed, it is usually due to extension from the cheeks and forehead. Any age can be affected including children, but the disease has a special predilection to involve individuals between the fourth and the sixth decades and is more common in males.4
The main presenting symptoms are tenderness, pain, fever, and malaise, which vary according to the virulence of the organism.4 A history of a scratch or an insect bite may be elicited from the patient, although in a significant proportion of patients, the portal of entry may not be obvious and no history of trauma is elicited.
The initial presentation is usually with a small, sharply defined, erythematous skin patch at the infected site, which looks like a rash but with a raised edge. If it starts in the cheek or the bridge of the nose, it may on occasion rapidly spread to involve the periorbital region, particularly the lower eyelids and the medial canthal area.14 The relatively diffuse nature of erysipelas is simply attributed to the clinical/pathogenic nature of the predominant causative organism (GAS).15 S. pyogenes remains the leading cause of both forms of diffuse cellulitis including erysipelas, in contrast to the other major skin pathogen S. aureus, which generally causes more localized disease (eg, abscess).15 The erythema is irregular with tongue-like extensions along the lymphatic vessels. The clinical appearance of an elevated, erythematous, indurated area with a sharp border is very characteristic, especially when tiny vesicles or bullae are seen at the advancing margin (Figure 61.1). In addition, the area is hot, edematous, and tender to touch. This tense edema gives the skin a shiny glazed appearance.10 In more severe cases, the skin can turn purple or black with blisters filled with fluid or blood (Figure 61.2). As the blisters rupture, raw areas of skin result. Regional lymphadenopathy usually accompanies the infection and local complications may include hemorrhagic infarction, skin ulceration, or necrosis.
Erysipelas is generally considered a nonculturable condition.10 Attempts to culture bacteria from the bullae, from tissue biopsies, or even from needle aspiration of saline-injected sites are usually unsuccessful because bacteria are present in small numbers.2 Imaging studies are also of no particular value in patients with erysipelas except to exclude a deeper extension of the infectious process.1
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