E S S E N T I A L S O F D I A G N O S I S
» Edematous, raised, circumscribed, hot, erythema-tous area, with or without vesicles or bullae.
» Central face or lower extremity frequently involved.
» Pain, chills, fever, and systemic toxicity may be striking.
» General Considerations
Erysipelas is a superficial form of cellulitis that is caused by beta-hemolytic streptococci.
» Clinical Findings
A. Symptoms and SignsThe symptoms are pain, malaise, chills, and moderate fever. A bright red spot appears and then spreads to form a tense, sharply demarcated, glistening, smooth, hot plaque.
The margin characteristically makes noticeable advances in days or even hours. The lesion is edematous with a raised edge and may pit slightly with the finger. Vesicles or bullae occasionally develop on the surface. The lesion does not usually become pustular or gangrenous and heals with-out scar formation. The disease may complicate any break in the skin that provides a portal of entry for the organism.
On the face, erysipelas begins near a fissure at the angle of the nose. On the lower extremity, tinea pedis with inter-digital fissuring is a common portal of entry.
B. Laboratory Findings
Leukocytosis is almost invariably present; blood cultures may be positive.
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Figure 6–28. Erythema migrans due to Borrelia burgdorferi (Lyme disease). (Courtesy of James Gathany, Public Health Image Library, CDC.)» Differential Diagnosis
Erysipeloid is a benign bacillary infection producing cel-lulitis of the skin of the fingers or the backs of the hands in fishermen and meat handlers.
» Complications
Unless erysipelas is promptly treated, death may result from extension of the process and systemic toxicity, par-ticularly in the elderly.
» Treatment
Intravenous antibiotics effective against group A beta- hemolytic streptococci and staphylococci should be consid-ered, but outpatient treatment with oral antibiotics has demonstrated equal efficacy. Oral regimens include a 7-day course with penicillin VK (250 mg), dicloxacillin (250 mg), or a first-generation cephalosporin (250 mg) orally four times a day. Alternatives in penicillin-allergic patients are clindamycin (250 mg twice daily orally for 7–14 days) or erythromycin (250 mg four times daily orally for 7–14 days), the latter only if the infection is known to be due to streptococci.
» Prognosis
With appropriate treatment, rapid improvement is expected. The presence of lymphedema carries the greatest risk of recurrence.
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2. Cellulitis
E S S E N T I A L S O F D I A G N O S I S
» Edematous, expanding, erythematous, warm plaque with or without vesicles or bullae.
» Lower leg is frequently involved.
» Pain, chills, and fever are commonly present.
» Septicemia may develop.
» General Considerations
Cellulitis, a diffuse spreading infection of the dermis and subcutaneous tissue, is usually on the lower leg (Figure 6–29) and most commonly due to gram-positive cocci, especially
group A beta-hemolytic streptococci and S aureus. Rarely, gram-negative rods or even fungi can produce a similar picture. In otherwise healthy persons, the most common portal of entry for lower leg cellulitis is toe web inter-trigo with fissuring, usually a complication of interdigi-tal tinea pedis. Other diseases that predispose to cellulitis are prior episodes of cellulitis, chronic edema, venous insufficiency with secondary edema, lymphatic obstruc-tion, saphenectomy, and other perturbations of the skin barrier. Bacterial cellulitis is almost never bilateral.
» Clinical Findings
A. Symptoms and SignsCellulitis begins as a tender small patch. Swelling, ery-thema, and pain are often present. The lesion expands over hours, so that from onset to presentation is usually 6 to 36 hours. As the lesion grows, the patient becomes more ill with progressive chills, fever, and malaise. Lymphangitis and lymphadenopathy are often present. If septicemia develops, hypotension may develop, followed by shock.
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Figure 6–29. Cellulitis. (Used, with permission, from Berger TG, Dept Dermatology, UCSF.)B. Laboratory Findings
Leukocytosis or at least a neutrophilia (left shift) is present from early in the course. Blood cultures may be positive. If a central ulceration, pustule, or abscess is present, culture may be of value. Aspiration of the advancing edge has a low yield (20%) and is usually not performed. In immunosup-pressed patients, or if an unusual organism is suspected and there is no loculated site to culture, a full thickness skin biopsy taken before antibiotics are given can be useful.
Either two specimens or one divided in half should be sent for routine histologic evaluation and for culture. Skin biopsy is particularly important in the immunocompro-mised patient in whom cellulitis may be due to an uncom-mon organism. If a primary source for the infection is identified (wound, leg ulcer, toe web intertrigo), cultures from these sites isolate the causative pathogen in half of cases and can be used to guide antibiotic therapy.
» Differential Diagnosis
Two potentially life-threatening entities that can mimic cellulitis (ie, present with a painful, red, swollen lower extremity) include deep venous thrombosis and necrotiz-ing fasciitis. The diagnosis of necrotiznecrotiz-ing fasciitis should be suspected in a patient who has a very toxic appearance, bullae, crepitus or anesthesia of the involved skin, overlying skin necrosis, and laboratory evidence of rhabdomyolysis (elevated creatine kinase [CK]) or disseminated intravas-cular coagulation. While these findings may be present with severe cellulitis and bacteremia, it is essential to rule out necrotizing fasciitis because rapid surgical debride-ment is essential. Other skin lesions that may resemble cellulitis include sclerosing panniculitis, an acute, exqui-sitely tender red plaque on the medial lower legs above the malleolus in patients with venous stasis or varicosities, and acute severe contact dermatitis on a limb, which produces erythema, vesiculation, and edema, as seen in cellulitis, but with itching instead of pain. Bilateral lower leg bacterial cellulitis is exceedingly rare and other diagnoses, especially severe stasis dermatitis (see Figure 12–1), should be con-sidered in this setting. Severe lower extremity stasis derma-titis usually develops over days to weeks rather than the hours of cellulitis. It is also not as tender to palpation as cellulitis. Cryptococcal cellulitis in the organ transplant recipient is often bilateral.
» Treatment
Intravenous or parenteral antibiotics may be required for the first 2–5 days, with adequate coverage for Streptococcus and Staphylococcus. Methicillin-susceptible S aureus (MSSA) can be treated with nafcillin, cefazolin, clindamycin, dicloxacillin, cephalexin, doxycycline, or TMP-SMZ. If MRSA is suspected or proven, treatment options include vancomycin, linezolid, clindamycin, daptomycin, doxycy-cline, or TMP-SMZ. In mild cases or following the initial parenteral therapy, dicloxacillin or cephalexin, 250–500 mg four times daily for 5–10 days, is usually adequate. In patients in whom intravenous treatment is not instituted, the first dose of oral antibiotic can be doubled to achieve
high blood levels rapidly. In patients with recurrent lower leg cellulitis (3–4 episodes per year), oral penicillin 250 mg twice daily can delay the appearance of the next episode.
» When to Admit
• Severe local symptoms and signs.
• SIRS criteria are met.
• Elevated white blood cell count with marked left shift.
• Failure to respond to oral antibiotics.
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