Epidemiology
Cellulitis is a common condition. The Global Burden of Disease study estimated that 56 million cases of cellulitis (678.4 per 100,000 population) occurred in 2021, causing 28,900 deaths.[1] One population-based study in Minnesota limited to cellulitis involving a lower extremity found an incidence of 199 episodes per 100,000 person-years.[2] In an Australian study, the overall annual incidence of primary episodes of lower limb cellulitis was 205 per 100,000 population.[3] Annual incidence of cellulitis in the Netherlands is estimated to be 22 per 1000 inhabitants.[4] In 2023 to 2024, more than 256,000 people were diagnosed with skin and soft tissue infections in England.[5]
Risk factors
Infections can occur when bacteria breach the skin surface, particularly where there is fragile skin or decreased local host defences.[20][21]
For information about history and examination of diabetic foot infections, see Diabetes-related foot disease.
Cellulitis following saphenous venectomy is a well-recognised association.[22][23] Chronic oedema resulting from other mechanisms also increases risk for cellulitis.[24] It is thought that the stasis causes impaired skin fragility, impairs immune response, and leads to stasis dermatitis, each of which can increase the risk of infection.
Lymphoedema, often following surgery and/or radiotherapy for a malignancy, has been associated with cellulitis in several settings, including lymph node dissection with or without irradiation for breast and gynaecological cancers.[24][25][26][27] The lymphatic impairment presumably renders local host defenses less effective, leading to subsequent infection.[14]
Infections can occur when bacteria breach the skin surface, particularly when skin has been damaged previously.[20] Recurrence is well documented and probably occurs due to persistence of other risk factors, such as lymphoedema, but inflammation with each acute episode may also lead to residual lymphatic dysfunction.[14][28]
Evidence of fungal infection (tinea) may reveal the point of bacterial entry.[29] Disruption of cutaneous barrier allows microorganism entry into tissue.[14] Pathogenic bacteria can be isolated from interdigital spaces in patients with tinea pedis interdigitalis.[19]
Fissures, scaling, and maceration may be a source of pathogen colonisation.[20]
People who inject drugs are at high risk of skin and soft tissue infections, due to a combination of factors, including local tissue injury and disruption to the cutaneous barrier, non-sterile injection, small vessell thrombosis and impaired lymphatic, and venous drainage.[30]
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