Cutaneous abscess and furuncle
A cutaneous abscess is a collection of pus in the dermis or subcutaneous tissue, and a furuncle (boil) is a perifollicular abscess most often caused by Staphylococcus aureus that can coalesce with adjacent furuncles into a carbuncle. Diagnosis is clinical from a tender, fluctuant nodule, and the essential first treatment for any fluctuant collection is incision and drainage, with oral antibiotics reserved for systemic signs, extensive surrounding cellulitis, immunocompromise, or an inadequate response to drainage alone.
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What this article covers
- Overview
Definition: a cutaneous abscess is a localized collection of pus in the dermis or subcutaneous tissue; a furuncle (boil) is a perifollicular cutaneous abscess arising at a hair follicle, most commonly from Staphylococcus aureus infection.
- Epidemiology
Common staphylococcal skin disease: furuncles and carbuncles are frequent presentations of Staphylococcus aureus skin infection across ambulatory and emergency settings.
- Risk factors
Diabetes mellitus and immunosuppression: impaired local and systemic host defenses increase susceptibility to staphylococcal follicular infection and abscess formation.
- Pathophysiology
Follicular origin: infection begins as folliculitis, inflammation and infection of a hair follicle, typically from Staphylococcus aureus.
- Clinical features
Diagnostic appearance: a painful, inflamed, often fluctuant nodule at a hair-bearing site, sometimes actively draining purulent material, is characteristic and diagnosis is based on this appearance.
- Differential diagnosis
Inflamed epidermoid (epidermal inclusion) cyst: a mobile dermal or subcutaneous nodule, usually with a central punctum, that is not centered on a hair follicle and, when infected, requires drainage…
- Diagnosis
Clinical diagnosis from appearance establishes the diagnosis first: a tender, fluctuant, hair-follicle-centered nodule, with or without spontaneous drainage, is diagnostic without further testing in a typical presentation.
- Management
First-line for every fluctuant lesion: incision and drainage.
- Complications
Local extension: untreated or inadequately drained infection can extend into surrounding cellulitis or deeper soft tissue.
- Prognosis
Favorable with drainage: most furuncles and abscesses resolve promptly once the collection is adequately drained, with or without adjunctive antibiotics.
- Prevention
Address modifiable risk factors: control of diabetes mellitus and reduction of skin occlusion or friction at affected sites lowers the risk of recurrent folliculitis progressing to furuncle.
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