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For further information, see CMDT PART 6-33: INFECTIOUS ERYTHEMAS

Key Features

Essentials of Diagnosis

  • 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

  • Usually due to gram-positive cocci, though gram-negative rods or even fungi can produce similar picture

  • The major portal of entry for lower leg cellulitis is toe web tinea pedis with fissuring of the skin at this site

  • Erysipelas is a superficial form of cellulitis that occurs classically on the cheek, caused by β-hemolytic streptococci (see Erysipelas)

Clinical Findings

Symptoms and Signs

  • Lesion begins as a small batch and expands over hours

  • Edematous, expanding, erythematous, warm plaque with or without vesicles or bullae

  • Pain at the lesion, malaise, chills, and moderate fever

  • Usually on the lower leg

  • Lymphangitis and lymphadenopathy may be present

  • Progressive chills, fever, and malaise

  • Septicemia and septic shock may develop

Differential Diagnosis

  • Deep venous thrombosis

  • Venous stasis

  • Candidiasis

  • Anthrax

  • Contact dermatitis

  • Herpes zoster (shingles)

  • Scarlet fever

  • Angioedema

  • Necrotizing fasciitis

  • Sclerosing panniculitis

  • Underlying osteomyelitis

  • Systemic lupus erythematosus

  • Erysipeloid


Laboratory Tests

  • Attempts to isolate the responsible organism by injecting and then aspirating saline are successful in 20% of cases

  • Leukocytosis and an increased sedimentation rate are almost invariably present but are not specific

  • Blood cultures may be positive

  • Skin biopsy is particularly helpful in an immunocompromised patient whose cellulitis may be due to an uncommon organism

Diagnostic Procedures

  • ALT-70 is a predictive model to diagnose cellulitis or a cellulitis mimic and to provide guidance about when a dermatology consultation is needed

    • Variables are

      • Asymmetry (3 points)

      • Leukocytosis of 10,000/mcL or more at presentation (2 points)

      • Tachycardia above 90 beats per minute (1 point)

      • Age 70 years or older (1 point)

    • Score above 5 carries more than an 82% chance of a true cellulitis while a score below 2 suggests a greater than 83% chance of a cellulitis mimicker



  • Intravenous or parenteral antibiotics effective against group A β-hemolytic streptococci and staphylococci may be required for the first 24–48 hours

  • Dicloxacillin or cephalexin, 250–500 mg four times daily orally for 5–10 days, is usually adequate for mild cases or following initial parenteral therapy

  • In patients in whom intravenous treatment is not instituted, the first dose of oral antibiotic can be doubled to achieve rapid high blood levels

  • Oral penicillin 250 mg twice daily or oral erythromycin 250–500 mg twice daily can decrease the risk of recurrence in patients with recurrent lower leg cellulitis (three to four ...

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