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Skin-nontumor / Clinical Dermatology

Infectious disorders

Carbuncle


Reviewer: Ha Kirsten Do, M.D., IUPUI (see Reviewers page)
Revised: 2 November 2010, last major update September 2010
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.

Definition
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● Deep form of bacterial folliculitis involving several hair follicles, often due to Staphylococcus aureus, which can be cultured from skin

Terminology
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● Also known as boils
Furuncle: small abscess exuding purulent material, involving skin and subcutis in areas with hair follicles
Carbuncle: aggregate of connected furuncles, involves multiple hair follicles

Epidemiology
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● Most individuals with carbuncles are otherwise healthy and have good personal hygiene, but they are among the 10-20% of population that are Staphylococcus aureus carriers on surface of skin
● Common in obese patients
● Carbuncles may occur in patients with immune deficiency, anemia, diabetes or iron deficiency

Sites
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Staphylococcus aureus is most commonly found in intertriginous regions (where two skin areas may touch or rub together) of nostrils, armpits, groin and intergluteal cleft

Etiology
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Staphylococcus aureus is present in patients in intertriginous regions, but may be transferred to other sites by scratching
● Tiny nicks or scratches in the skin can inoculate the bacteria into the wall of a hair follicle, a weak point in the skin
● Once innoculated, bacteria cause a boil, which runs its usual infectious course in about 10 days

Clinical
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● Painful localized bacterial infection of skin and subcutis, usually with several openings through which pus is discharged

Treatment
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● Antiseptic cleanser, like povidone-iodine or chlorhexidine is used daily for several weeks to clean carbuncle
● Topical antibiotics include erythromycin BID and clindamycin BID to affected area until clear

Note: verify current drug dosages before use (eMedicine)

Oral antibiotics include:
● Cephalexin (adult) 1-4 g/day divided BID or QID x 10-14 days; (children) 25-50 mg/kg/day PO divided q6H for mild to moderate infection; 50-100 mg/kg/day divided q6H for severe infection; not to exceed 4g/day for any age
● Dicloxacillin (adult or children >40 kg) 125-500 mg q6h x 10-14 days; (children <40 kg): 12.5-50 mg/kg/d PO divided q6h
● Erythromycin (adult) 500 mg BID or 330mg q8hr x 10-14 days
● Clindamycin (adult) 150-450 mg q6-8h x 10-14 days; (children) 10-30 mg/kg/day q6-8h
● Minocycline (adult) 100 mg BID x 10-14 days
● Rifampin (adult) 600 mg qD x 10 days; (children) 15 mg/kg/day divided BID x 10 days
● Ciprofloxacin (adult): 250-750 mg BID x 10-14 days

● In recurrent cases, obtain nasal culture of patient and family members to look for Staphylococcus aureus colonization
● If patient is Staphylococcus aureus nasal carrier, consider applying topical antibiotic like mupirocin ointment to nostrils twice daily for 5 days (Wikipedia)

● If family members are nasal carriers, consider mupirocin ointment or rifampin 600 mg daily for 10 days
● Consider checking nasal swab for MRSA or culture for sensitivity for treatment failure

Prevention:
● Good hygiene including bathing, hand-washing, keeping nails short and clean
● Avoid close shaving until lesions are completely resolved
● Change disposable razors daily or clean electric razor heads daily
● Wear loose-fitting clothes (tight-fitting clothes may cause occlusion); change clothes daily
● In obese patients, weight reduction will be beneficial

Clinical description
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● Tender, swollen red papules or pustules

Clinical images
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Various images

Micro description
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● Inflammatory cells, predominantly neutrophils, within the wall and ostia of the hair follicle, creating a follicular-based pustule
● Inflammation can be either limited to the superficial follicle, primarily involving the infundibulum, or can affect both the superficial and deep aspects of the follicle
● Deep folliculitis can arise from the chronic lesions of superficial folliculitis or from lesions that are manipulated or scratched; may cause scarring

Virtual slides
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Carbuncle

Differential diagnosis
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Abscess / furuncle
Folliculitis: tender pustule that involves the hair follicle
Irritated epidermal inclusion cyst

End of Skin-nontumor / Clinical Dermatology > Infectious disorders > Carbuncle


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