Core Dermatology Diagnoses / CategoriesInfectious

Cellulitis

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Publish date: Posted on
Last updated: February 17, 2024

Keywords #

cellulitis
purulent cellulitis

Diagnosis #

Cellulitis is an infection of the deep dermis and subcutaneous tissue, typically secondary to a breakdown in the skin from trauma, eczema, or ulceration. It is a common infection most often caused by Streptococcus pyogenes or Staphylococcus aureus.[2] It may rapidly progress to sepsis or may extend to deeper tissues, resulting in necrotizing fasciitis, osteomyelitis, meningitis, or endocarditis.[1-3] Consequently, cellulitis should be treated promptly with antibiotics.

Key Concepts #
  • Cellulitis is a common skin infection of the deep dermis.
  • It is found in all age groups, though it is most common in older adults.
  • S. pyogenes and S. aureus are the most commonly implicated pathogens.
  • Potential complications may be severe and life threatening, making prompt treatment essential.
  • Antibiotics with coverage for S. pyogenes and S. aureus should be started empirically based on clinical diagnosis.
  • MRSA coverage may be considered based on patient risk factors.
Epidemiology #

Cellulitis is a common infection accounting for approximately 10% of infectious disease hospitalizations in the United States every year.[2] While it is most common in older adults, it affects patients of all ages and races. Risk factors for cellulitis include lymphedema, venous stasis, immunosuppression, chronic conditions such as diabetes, recent injury, previous history of cellulitis, obesity, pregnancy, and substance use.[3]

Clinical Features #
  • Poorly demarcated erythema, swelling, and tenderness.
  • May have skin dimpling (“peau d’orange”), bullae, or ulceration.
  • Typically unilateral, most often affecting the lower extremities.
  • Lymphadenopathy and streaking are common.
  • May present with fever, chills, and/or rigors, secondary to bacteremia.
Differential Diagnoses #
Diagnostic Workup #

Cellulitis is usually a clinical diagnosis and further workup is often unnecessary for uncomplicated, non-purulent cellulitis. If the patient is at increased risk for complications, such as immunosuppressed patients, needle aspiration or punch biopsy may be used to obtain samples for culture. Culture from a swab of an area of broken skin is of little utility, as it is typically contaminated with normal skin flora. If the cellulitis is purulent, the exudate should be swabbed and cultured.[2]

Labs such as a CBC, CRP, or ESR will show evidence of infection and inflammation.[3]These findings, however, are not specific to cellulitis and of little clinical use.

Treatment #

Initiation of empiric antibiotics with S. pyogenes coverage is the recommended treatment for cellulitis. While oral cephalexin or IV cefazolin are commonly used, antibiotics should be chosen based on local susceptibilities and protocols. An oral antibiotic course of five to 10 days is recommended for uncomplicated cellulitis, with a shorter course being preferable unless the patient is immunosuppressed or not showing resolution of symptoms within five days of treatment.[2]

Patients should show symptomatic improvement within the first48-72 hours of treatment. If they have not, expanded coverage of MRSA should be considered. Empiric treatment for MRSA is typically not required unless the patient has specific risk factors such as recent hospitalization, indwelling medical devices, sepsis, or prior history of MRSA infection.[4]

Slide Viewer #
https://utahderm.med.utah.edu/image-viewer/
References #
  1. McAdam, Alexander J., et al. Robbins and Cotran Pathologic Basis of Disease, by Abul K. Abbas et al., 9th ed., Elsevier/Saunders, 2015, pp. 364–365.
  2. Raff, Adam B., and Daniela Kroshinsky. “Cellulitis.”JAMA, vol. 316, no. 3, 19 July 2016, pp. 325–337., doi:10.1001/jama.2016.8825.
  3. Stanway, Amy. “Cellulitis.” Edited by Jannet Gomez and Amanda Oakley, Cellulitis | DermNet NZ, dermnetnz.org/topics/cellulitis/.
  4. Stevens, Dennis L., et al. “Executive Summary: Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America.” Clinical Infectious Diseases, vol. 59, no. 2, 15 July 2014, pp. 147–159., doi:10.1093/cid/ciu444.
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