Folliculitis Clinical Presentation

Patients with superficial folliculitis typically report an acute onset associated with pruritus or mild discomfort. 

Patients with deep folliculitis usually have longer-standing lesions and more often report pain and sometimes suppurative drainage. Persistent or recurrent lesions may result in scarring and permanent hair loss. Patients may also develop folliculitis following laser epilation. ^[33]

The follicular papulopustular eruption secondary to epidermal growth factor receptor inhibitors usually presents within the first 2-weeks of initiation of therapy. Typically it occurs on the face, scalp, chest, and upper back and is often associated with pruritus, pain, and desquamation. The eruption is dose-dependent and peaks after 3-4 weeks of therapy. Although, the eruption can negatively affect the quality of life of some patients, some authors believe the acneiform eruption also seems to correlate with a good response to therapy. ^{[9, 10]}

Patients with superficial folliculitis usually present with multiple small papules and pustules on an erythematous base that are pierced by a central hair, although the hair may not always be visualized. Deeper lesions manifest as erythematous, often fluctuant, nodules. Sometimes, a patterned folliculitis occurs in areas that were shaved or occluded. Any hair-bearing site can be affected, but the sites most often involved are the face, scalp, thighs, axilla, and inguinal area.

Folliculitis has been traditionally divided into superficial and deep forms; however, most superficial forms can evolve into the deep form. The most common superficial form of infectious folliculitis is known as impetigo of Bockhart, barbers itch, or folliculitis barbae and is caused by Staphylococcus aureus, such as the infection shown in the image below. The lesions are seen in the bearded area, often on the upper lip near the nose, as erythematous follicular-based papules or pustules that occur in crops and may rupture leaving a yellow crust. The pustule is often pierced by a hair that is easily extracted from the follicle. This form of folliculitis occurs more commonly in carriers of nasal staphylococci. 

Another type of superficial folliculitis caused by staphylococci is a sty, which only differs from typical folliculitis in that it occurs on the eyelid. ^[31]

When involvement of the follicle is more extensive, a follicular-centered dermal abscess develops. When this occurs in the beard areas of the face, it is referred to as sycosis barbae (vulgaris), but if it occurs elsewhere, it is referred to as a furuncle or boil. A confluence of several furuncles results in a carbuncle. ^{[14, 31]}

Tinea barbae is an uncommon form of superficial folliculitis that clinically resembles its bacterial counterpart; however, it is caused by a superficial infection by various zoophilic dermatophytes. This superficial fungal folliculitis is most commonly seen in male farmers who have direct contact with an animal and typically affects one side of the face in the submaxillary region or chin.

Patients with more extensive involvement of the follicle or those who experience an exaggerated hypersensitivity reaction to the dermatophyte infection present with enlarged, boggy purulent plaques, called kerions, in the site of the prior superficial infection. Another type of deep fungal folliculitis called Majocchi granuloma classically occurs after treatment of a superficial fungal infection with steroids and occlusion or on the legs of women from shaving.

Gram-negative folliculitis primarily occurs in patients on long-term antibiotic therapy, most often in patients treated for acne. This type of folliculitis arises from disequilibrium of the normal skin bacteria in favor of gram-negative organisms such as Enterobacter, Klebsiella, Escherichia, Serratia,Morganella, ^[15] and Proteus species. These lesions manifest as multiple small pustules that are most pronounced in the perinasal region and can spread to the chin and cheeks. Approximately 4% of acne patients treated with systemic antibiotics develop gram-negative folliculitis. ^{[31, 34]}

Pseudomonal folliculitis is another gram-negative folliculitis and is also known as hot tub (spa) folliculitis and wet suit folliculitis (see the images below). It appears 8-48 hours after exposure to contaminated water or wet suits as erythematous follicular-based papules and pustules that are most concentrated in areas occluded by swimwear. This form of folliculitis may be associated with systemic findings such as fever, headache, sore throat, malaise, or gastrointestinal distress, but it is a self-limited condition that resolves in 7-14 days. Aeromonas folliculitis is also associated with water exposure. ^[16]

Another similar condition is Pseudomonas hot hand-foot syndrome, which occurs in a similar clinical situation but eventuates in painful erythematous nodules and papules on the palms and soles rather than folliculitis. ^[17]

Pityrosporum folliculitis, typically seen in young adults, with a slight female predominance, presents as intensively pruritic small uniform papules and pustules on the back, chest, and shoulders. Facial involvement may resemble monomorphous acne and may have less pruritus. ^[32] It occurs more often in warm, humid climates and may be more frequent in immunocompromised patients or in patients on long-term antibiotics. This eruption is due to follicular infection by Malassezia furfur, which is a lipophilic yeast. ^[26]

An unusual cause of folliculitis occurs as a result of either overgrowth of Demodex mites or an acquired hypersensitivity to the mite. This form of folliculitis manifests with a more diffuse background erythema, in addition to the follicular-centered papules and pustules. ^{[18, 30]} This is most commonly seen in immunosuppressed patients.

An uncommon form of folliculitis is due to an infection with herpes viruses. This form of folliculitis can be caused by an infection by herpes simplex viruses 1 and 2 and is found in areas adjacent to a primary cold sore. It is spread by shaving. These lesions appear as grouped or scattered vesicles. ^{[19, 20]}

Varicella-zoster virus may present with exclusive follicular involvement.  Most patients present with erythematous hyperkeratotic papules in a dermatomal distribution; however, dissemination can occur in immunocompromised patients. ^[21] In contrast to the characteristic lesions seen in most herpes infections, vesicles typically do not occur. Biopsy is often required to confirm the diagnosis. ^[20]

Folliculitis can also have a noninfectious etiology caused by follicular trauma or occlusion or may be idiopathic. For example, pseudofolliculitis barbae, also known as shaving or razor bumps, occurs primarily in the bearded area of African American males or other racial groups with thick, coarse, curly hair. ^[29] This condition is not a folliculitis per se, but rather a perifolliculitis that arises as a result of the hair reentering the skin adjacent to its exit point from the follicle. The hair then acts as a foreign body and incites inflammation. The inflammation can spontaneously resolve if the hair is extracted or it can become associated with a chronic foreign body granulomatous reaction and may result in scarring.

Acne keloidalis nuchae is a similar condition that arises on the neck and occipital region of the scalp. This condition tends to be more chronic and has greater potential for scarring. ^[27]

Acute generalized exanthematous pustulosis and anticonvulsant hypersensitivity syndrome both manifest as an acute onset of a discrete pustular eruption arising shortly after beginning therapy with various medications. Although the eruption that occurs in acute generalized exanthematous pustulosis is often differentiated from anticonvulsant hypersensitivity syndrome by having nonfollicular-based pustules, either condition can have follicular or nonfollicular-based pustules.

Papulopustular drug eruption due to EGF-R is a relatively new entity and consists of a follicular eruption on the face, chest, and upper back that occurs approximately 2 weeks after initiation of chemotherapy. It is seen in up to 90% of patients taking EGF-R inhibitors, and its presence correlates to a positive response to chemotherapy. ^{[7, 8, 22]} Effective management can be critical to compliance with the anticancer treatment regimen.

The last noninfectious folliculitis to be discussed is eosinophilic folliculitis. It manifests as intensely pruritic pustules and can occur in at least 3 different clinical situations. The first is the original description of eosinophilic pustular folliculitis, also known as Ofuji disease. It arises in Japanese males at an average age of 30 years. The lesions initially begin as discrete papules and pustules that eventually coalesce to form circinate plaques composed of a peripheral rim of pustules with central clearing; however, granulomatous lesions have also been described. ^[6] These lesions appear cyclically on the face, back, and extensor surfaces of the arms and spontaneously resolve in 7-10 days. Often, peripheral eosinophilia is present. ^[13]

A second form of eosinophilic folliculitis arises in patients with AIDS and other conditions that result in immunosuppression. ^[23] This form is seen most often in adult males with a CD4⁺ count of less than 300 cells/μL. It is persistent and does not form an annular pattern. The lesions tend to favor the face, scalp, and upper trunk. ^[4] Eosinophilic folliculitis may also occur after antiretroviral therapy, possibly through macrophage activation. ^[5]

The last form of eosinophilic folliculitis occurs in infants. It is more common in male infants and usually is self-limited; however, as in Ofuji disease, it may follow a cyclic course lasting months to years. Unlike the adult form, the lesions primarily affect the scalp and eyebrows and are often associated with secondary crusting. This form may also be associated with peripheral eosinophilia.

In 2010, a report described hypertrophic scars from surgical staples that mimicked folliculitis. ^[24]

Complications from folliculitis are uncommon; however, persistent and deep folliculitis can result in cellulitis, furunculosis, scarring, sinus tract formation, and permanent hair loss.