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Skin-nontumor / Clinical Dermatology

Infectious disorders


Reviewer: Ha Kirsten Do, M.D., IUPUI (see Reviewers page)
Revised: 10 November 2010, last major update September 2010
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.


● Primary inflammation of a hair follicle, either infectious or noninfectious


Perifolliculitis: presence of inflammatory cells in the perifollicular tissues that may involve the adjacent reticular dermis; either primarily lymphocytic (lichen planopilaris, pityriasis rubra pilaris) or granulomatous (perioral dermatitis, rosacea)
Pseudolymphomatous folliculitis: facial lesion with dense, polymorphic, mixed lymphocytes around hair follicles and infiltrating follicular epithelium


● Common sites are the face, scalp, thighs, axilla and inguinal area


● Caused by infection, friction and other causes of follicular trauma, excessive perspiration and occlusion
● Infectious cases are either superficial (fungi, bacteria, syphilis, viral) or deep (usually granulomatous and due to either fungi or bacteria)
● Fungal forms may be endothrix (spores are within hair shaft) or ectothrix (spores are on outer surface of hair shaft)
● Noninfectious cases are either superficial/suppurative (acne vulgaris, rosacea, follicular mucinosis, steroid-induced), deep/granulomatous (acne vulgaris-conglobate and keloidal forms or perforating) or spongiotic (Fox-Fordyce disease, atopic dermatitis, pruritic folliculitis of pregnancy)
● Epidermal growth factor receptor (EGFR) inhibitors appear to be relevant in folliculitis by causing abnormal epidermal differentiation that leads to follicular obstruction and subsequent inflammation (Br J Dermatol 2001;144:1169)

Clinical features

● Superficial folliculitis is more common but is often self-limited
● Patients with recurrent or persistent superficial folliculitis or with deep folliculitis are more likely to seek medical care
● In recalcitrant folliculitis that failed standard therapy, consider cultures for sensitivity, Gram stain, potassium chloride (KOH) preparation to rule out fungal folliculitis
● Clinical presentation of superficial folliculitis is acute onset of mildy tender papules and pustules
● Deep folliculitis is usually associated with more pain and may have suppurative drainage; may cause scarring and permanent hair loss


● For uncomplicated superficial folliculitis, use antibacterial soaps, good handwashing
● For recurrent and deep lesions, treat empirically with topical antibiotics
● Antiobiotics should kill Staphylococcus aureus, the most common pathogen; recommended to use dicloxacillin and cephalosporins (eMedicine)
● For MRSA, use clindamycin, bactrim, minocycline or linezolid
● For Staphylococcus aureus carriers, treat patient and family with mupirocin ointment BID x 5 days or rifampin 600mg/day x 10 days

Clinical images


Various images

Micro description

● Superficial folliculitis has moderate inflammatory cells in the follicular ostium and upper regions of the follicle
● Infiltrate initially consists of neutrophils, later becomes more mixed with lymphocytes and macrophages

Micro images


Various images

Differential diagnosis

● Acne vulgaris
● Acneiform eruptions
● Cutaneous candidasis
● Coccidiomycosis
● Dermatologic manifestations of renal disease
● Erythema toxicum neonatorum
● Fire ant bites
● Fox-Fordyce disease
● Graham-Little-Piccardi-Lasseur syndrome
● Id-reaction (autoeczematization)
● Impetigo
● Insect bites
● Irritant contact dermatitis
● Milia
● Perioral dermatitis
● Popular urticaria
● Pruritic popular eruption of HIV disease
● Rosacea
● Seabatherís eruption
● Subcorneal pustular dermatosis

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

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