This woman has a carbuncle. It is usually secondary to Staphylococcus aureus infection of adjacent interconnecting pilosebaceous units. Treatment includes incision and drainage, warm compresses, and systemic antibiotics aimed against S. aureus.
The skin is comprised of two layers, the epidermis and the dermis. The epidermis is the superficial layer that contains four distinct cell types: keratinocytes, melanocytes, Langerhans' cells, and Merkel cells. Keratinocytes make up the majority of the cells, and are arranged in four layers. The stratum basale is the deepest layer, and is made up of continually dividing cells that then migrate up to eventually form the most superficial layer, the stratum corneum. These cells eventually desquamate and slough such that the epidermis “turns over” approximately every 30 days.
The epidermis attaches to the deeper dermis by a complex structure referred to as the basement membrane. The dermis is the deeper layer of skin and consists of two layers, the superficial papillary dermis and the deeper reticular dermis. The dermis consists of collagen, elastic tissue, and cells all embedded within the ground substance. Also located within the dermis are the blood vessels, sweat glands, and nerves. Deep to the dermis is the subcutaneous fat.
The pilosebaceous unit is located deep in the skin. It is comprised of the hair bulb, the hair follicle, the sebaceous gland, the sensory end organ, and the arrector pili muscle. The sebaceous gland adjacent to the follicle produces sebum, an oily substance of fat and epithelial debris. Folliculitis refers to inflammation of the hair follicle with subsequent blockage of the sebaceous gland. The result is mild pain or itching with small red papules or pustules surrounding a hair shaft. They are usually located in areas where short coarse hair predominates, such as a man's beard. Localized uncomplicated folliculitis can be treated with warm compresses, gentle cleansing with antibacterial soap, or topical benzoyl peroxide. Addition of topical antibiotics such as mupirocin ointment also may be initiated, but often is not required. If there is extensive or refractory folliculitis, anti-staphylococci systemic antibiotics should be initiated.
Hot tub folliculitis is caused by Pseudomonas aerugenosa. A patient typically presents six to 72 hours after being in a hot tub or warm pool with itchy red papules of the trunk or extremities. Any warm and moist environment can allow Pseudomonas to proliferate. Patients who use a loofah when bathing also may develop this infection. It typically resolves spontaneously after removing the offending agent. For mild cases, treatment includes local skin cleansing plus or minus a topical antibiotic ointment such as 0.1% polymyxin B. For severe or refractory cases, oral ciprofloxacin for seven to 10 days is the drug of choice in adults and an anti-pseudomonas semi-synthetic penicillin in children.
A furuncle or boil is an extension of folliculitis into the subcutaneous tissue. It manifests as a red, deep-seated, painful nodule usually 1–5 mm in size adjacent to a hair follicle. It frequently becomes fluctuant, may drain spontaneously, or may ulcerate. Like a simple folliculitis, the infecting organism is usually S. aureus, which can hematogenously spread to affect the heart, kidneys, and bone. Treatment of an uncomplicated furuncle in an immunocompetent individual usually requires incision and drainage and local warm compresses. If there is surrounding cellulitis or any systemic signs of infection, oral antibiotics should be initiated. Traditionally a first-generation cephalosporin such as cephalexin was the initial drug of choice, but with the development of community-acquired methicillin-resistant S. aureus, empiric therapy has shifted to the use of antibiotics other than beta-lactams (i.e., trimethoprim-sulfamethoxazole, tetracyclines, and clindamycin).
It should be mentioned that community-acquired MRSA is different from nosocomial MRSA not only in its susceptibility to antibiotics other than beta-lactams but also in the patient population affected. Community-acquired MRSA typically affects young healthy patients and in particular those sharing sporting equipment and clothing.
A carbuncle results when individual furuncles coalesce secondary to the destruction of the underlying fibrous connective tissue. The result is a larger painful nodule with deep interconnected sinus tracts and abscesses. A common place for their formation is at the nape of the neck, as the patient presented in this case. As with a furuncle, incision and drainage is often required with attention paid to gentle blunt dissection to break up loculations. Warm compresses and oral antibiotics such as those described above for the treatment of furuncles should be initiated. Complicated cases and those involving patients with immunodeficiency should be admitted for intravenous antibiotics.
Patients with recurrent furuncles or carbuncles should be evaluated for nasal colonization with S. aureus. Intranasal application of mupirocin or bacitracin ointment twice a day for five to seven days helps decrease colonization and subsequent infection. Other regimes include oral clindamycin 150 mg a day for three months, rifampin 600 mg a day for seven to 10 days, or cloxacillin 500 mg four times a day for seven to 10 days.