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Cellulitis in Adult

See also in: Cellulitis DDx,Anogenital,Hair and Scalp,Oral Mucosal Lesion
Contributors: Negar Esfandiari MD, Sabrina Nurmohamed MD, Susan Burgin MD, Paritosh Prasad MD
Other Resources UpToDate PubMed

Synopsis

Cellulitis is a common bacterial infection of the deep dermis and subcutaneous tissue characterized by erythema, pain, warmth, and swelling. Pathogens causing cellulitis are strongly correlated with age and immune status:
  • Immunocompetent adults: common etiologies include Staphylococcus aureus (particularly if there is concurrent purulence) and Streptococcus pyogenes.
  • Immunocompromised individuals: common pathogens such as S aureus and Streptococcus should be considered, but gram-negative pathogens should also be considered and covered.
  • Diabetic foot infections and decubitus ulcers: consider a mixture of gram-positive cocci and gram-negative aerobes and anaerobes.
  • Aquatic soft tissue injury: Vibrio spp, Aeromonas spp, Mycobacterium marinum, etc.
A focused history should determine immune status, comorbid conditions, possible sites and causes of skin barrier disruption, prior history of cellulitis, and methicillin-resistant S aureus (MRSA) risk factors, as well as community prevalence of MRSA. The most common route of bacterial seeding in immunocompetent individuals is via direct inoculation, and in immunocompromised individuals, it is via hematogenous seeding.

Risk factors for developing cellulitis include minor skin trauma, atopic dermatitis, contact dermatitis, body piercings, intravenous (IV) drug use, tinea pedis infection, animal bites, peripheral vascular disease, obesity, older age, immune suppression (chronic systemic steroid use, neutropenia, immunosuppressive medications, organ transplantation, HIV), and lymphatic damage (lymph node dissection, radiation therapy, vein harvest for coronary artery bypass surgery / saphenous venectomy, and damage that occurs following multiple prior episodes of cellulitis).

Fevers, chills, and malaise may precede the onset of cellulitis but may also be absent. Poorly defined borders, erythema, swelling, tenderness, and warmth characterize typical cellulitis lesions. In adults, the extremities, particularly the lower extremities, are the most common sites affected. In more severe cases, additional clinical features may include vesicle and bullae formation, pustules, and necrosis. Complications are not common but can include glomerulonephritis, lymphadenitis, and bacteremia.

A rising prevalence of MRSA has been identified as a pathogen of skin and soft tissue infections in otherwise healthy individuals lacking the aforementioned risk factors for cellulitis. MRSA should be considered for penetrating traumas, purulent infections, and in specific populations: athletes, children, prisoners, military service members, long-term care residents, and IV drug users. Other MRSA risk factors include recent admission to a health care facility, presence of an indwelling catheter, poor personal hygiene, and history of MRSA.

Recurrent Cellulitis: Major risk factors for recurrent cellulitis include chronic edema, dermatomycosis, and lymphatic or venous insufficiency. Prior episodes of cellulitis, immunodeficient states, obesity, previous local surgery / saphenectomy, as well as having cancer, can also increase the risk of recurrent cellulitis.

Note: It is exceedingly rare for cellulitis to occur bilaterally simultaneously, so if redness and involvement of the legs are bilateral in a patient suspected to have cellulitis, consider an alternative diagnosis such as stasis dermatitis or contact dermatitis (allergic, irritant).

Related topics: orbital cellulitis, preseptal cellulitis

Codes

ICD10CM:
L03.90 – Cellulitis, unspecified

SNOMEDCT:
128045006 – Cellulitis

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Differential Diagnosis & Pitfalls

Cellulitis can be caused by many different bacterial pathogens, but the diagnosis is almost always made clinically. If a patient has had more than 1 episode of cellulitis, investigate risk factors for recurrent cellulitis but also consider alternative diagnoses.

Stasis dermatitis is a frequent cause of bilateral leg redness. There are usually no systemic signs or leukocytosis; it is commonly bilateral with pruritus and red-brown dyspigmentation.

The differential for cellulitis is vast, and time course, drug / exposure history, and the presence / absence of systemic features should help delineate the cause. Below are common differential diagnoses:

Deep tissue infection
  • Myonecrosis (Gas gangrene)
  • Necrotizing fasciitis
Infectious
  • Erysipelas
  • Arthropod bite or sting
  • Flexor tenosynovitis (see Tenosynovitis, Trigger finger)
  • Herpes zoster
  • Herpes simplex virus
  • Skin bacterial abscess
  • Erythema migrans of Lyme disease
  • Septic arthritis
Inflammatory
  • Chemical cellulitis / extravasation injury
  • Eosinophilic cellulitis (eosinophilic cellulitis)
  • Atopic dermatitis
  • Contact dermatitis (Allergic contact dermatitis, Irritant contact dermatitis)
  • Phytophotodermatitis
  • Acute febrile neutrophilic dermatosis
  • Panniculitides, such as Erythema nodosum
  • Polyarteritis nodosa
  • Familial Mediterranean fever
  • Fixed drug eruption
  • Angioedema
Vascular
  • Stasis dermatitis
  • Acute Lipodermatosclerosis
  • Superficial thrombophlebitis
  • Deep vein thrombosis
  • Lymphedema
  • Calciphylaxis
  • Hematoma
  • Erythromelalgia
Other
  • Gout
  • Fixed drug eruption
  • Toxic erythema of chemotherapy
  • Complex regional pain syndrome
  • Extramammary Paget disease
  • Carcinoma erysipeloides
  • Foreign body granuloma

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Last Reviewed:03/13/2023
Last Updated:04/02/2023
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Cellulitis in Adult
See also in: Cellulitis DDx,Anogenital,Hair and Scalp,Oral Mucosal Lesion
A medical illustration showing key findings of Cellulitis (General) : Chills, Lymphadenopathy, Lymphangitis, Skin warm to touch, Unilateral distribution
Clinical image of Cellulitis - imageId=51043. Click to open in gallery.  caption: 'Linear erythematous plaques on the thigh (lymphangitis) indicating proximal spread of a more distal cellulitis.'
Linear erythematous plaques on the thigh (lymphangitis) indicating proximal spread of a more distal cellulitis.
Copyright © 2024 VisualDx®. All rights reserved.