Background
Folliculitis is defined histologically as the presence of inflammatory cells within the wall and ostia of the hair follicle, creating a follicular-based pustule. The actual type of inflammatory cells can vary and may be dependent on the etiology of the folliculitis, the stage at which the biopsy specimen was obtained, or both. The inflammation can be either limited to the superficial aspect of the follicle with primary involvement of the infundibulum or the inflammation can affect both the superficial and deep aspect of the follicle. Deep folliculitis can eventuate from chronic lesions of superficial folliculitis or from lesions that are manipulated, and this may ultimately result in scarring.
Perifolliculitis, on the other hand, is defined as the presence of inflammatory cells in the perifollicular tissues and can involve the adjacent reticular dermis. Folliculitis and perifolliculitis can manifest independently or together as a result of follicular disruption and irritation.
Acne represents a noninfectious form of folliculitis. The follicular inflammation seen in acne occurs as a secondary event as a result of follicular obstruction from abnormal keratinization. In acne, the superficial aspect of the follicle distends and is obstructed by a keratin plug. The sebum fills the follicle, and the normally commensal bacteria (Propionibacterium acnes) produces excess free fatty acids, which trigger follicular inflammation.
Acne-related eMedicine articles include Acne Conglobata, Acne Fulminans, Acne Keloidalis Nuchae, Acne Vulgaris, and Acneiform Eruptions.
Pathophysiology
Folliculitis is a primary inflammation of the hair follicle that occurs as a result of various infections, or it can be secondary to follicular trauma or occlusion.
Eosinophilic folliculitis differs in that it is thought to occur as a result of an autoimmune process directed against the sebocytes or some component of the sebum.
Although the etiology of papulopustular eruption secondary to epidermal growth factor receptor (EGF-R) inhibitors is unknown, it is hypothesized to occur secondary to abnormal epidermal differentiation that leads to follicular obstruction and subsequent inflammation.[1, 2]
Epidemiology
Frequency
United States
Superficial folliculitis is common, but because it is often self-limited, patients rarely present to the doctor. Those who are seen more often have either recurrent/persistent superficial folliculitis or have deep folliculitis. Although the incidence is unknown, certain conditions make patients more susceptible. These include frequent shaving, immunosuppression, preexisting dermatoses, long-term antibiotic use, occlusive clothing and/or occlusive dressings, exposure to hot humid temperatures, diabetes mellitus, obesity, and use of EGF-R inhibitor medications.
Folliculitis has been reported following smallpox or anthrax vaccine. These cases may become more common because more military troops are being deployed.[3]
Mortality/Morbidity
Although complications from folliculitis are uncommon, they include cellulitis, furunculosis, scarring, and permanent hair loss.
Race
Folliculitis occurs in persons of any race, but pseudofolliculitis and traction folliculitis occurs more commonly in African Americans and classic eosinophilic folliculitis is more common in Japanese persons.[4, 5]
Sex
For most cases of folliculitis, no data are available to indicate the presence of a sexual predilection; however, eosinophilic folliculitis is reported to more frequently affect males and Pityrosporum folliculitis may have a slightly increased female incidence.
Age
Folliculitis can be seen in persons of all ages.
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