Approach Considerations
In classic erysipelas, no laboratory workup is required for diagnosis or treatment. However, leukocytosis and elevations in erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are common. [1, 15] Routine blood and tissue cultures are not cost-effective, because they have an extremely low yield and the results have minimal impact on management.
Imaging studies are not usually indicated and are of low yield. Magnetic resonance imaging (MRI) and bone scintigraphy are helpful when early osteoarticular involvement is suspected. In this setting, standard radiographic findings typically are normal.
Bacterial Cultures
Bacterial cultures are positive in only 5% of cases, and tissue Gram stain and culture are generally not helpful. However, bacterial cultures may be useful when the diagnosis is in question or when concern for bacteremia and metastatic infection exists.
Cultures may be of benefit in patients with prosthetic heart valves, other intravascular devices, artificial joints, and in immunocompromised or toxic-appearing patients. Bacterial cultures from the portal of entry may be most helpful, especially in persons with atypical clinical presentations. [16]
Histologic Findings
The histologic hallmarks of erysipelas are marked dermal edema, vascular dilatation, and streptococcal invasion of lymphatics and tissues. This bacterial invasion results in a dermal inflammatory infiltrate consisting of neutrophils and mononuclear cells. The epidermis is often secondarily involved. Rarely, bacterial invasion of local blood vessels may be seen.
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Well-demarcated, erythematous plaque of erysipelas. Courtesy of the US Centers for Disease Control and Prevention.
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Facial erysipelas exhibiting classic fiery-red plaque with raised, well-demarcated borders.
