carbuncles
Summary
A carbuncle is a deep, coalescing cluster of infected hair follicles forming a single inflammatory mass that drains through multiple openings. It is usually caused by Staphylococcus aureus and typically requires incision and drainage plus antibiotics.
Detail
The follicular infections form a progression: folliculitis is superficial inflammation of a single follicle; a furuncle, or boil, is a deeper abscess of one follicle and its surrounding tissue; and a carbuncle is several adjacent furuncles that merge into a deeper, multiloculated lesion with several draining sinuses. Carbuncles occur most often on the back of the neck, upper back, and thighs, and unlike simple furuncles they commonly produce fever and malaise and may lead to bacteraemia. Predisposing factors include diabetes mellitus, obesity, immunosuppression, and nasal carriage of S. aureus, which is present in roughly a third of people; recurrent disease warrants decolonization with intranasal mupirocin and chlorhexidine washes. Management is incision and drainage, which is the definitive treatment for any abscess, with systemic antibiotics covering MRSA — trimethoprim-sulfamethoxazole, doxycycline, or clindamycin — for larger lesions, surrounding cellulitis, or systemic features. Facial lesions in the danger triangle risk cavernous sinus thrombosis via the valveless facial veins.
Sources
- Harrison's Principles of Internal Medicine
- First Aid for the USMLE Step 1
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