Folliculitis decalvans

INTRODUCTION — Folliculitis decalvans (FD) is a rare, chronic cicatricial (scarring) alopecia that occurs in adults and classically presents as an expanding patch of alopecia with peripheral pustules on the scalp (picture 1A-B). Patients may experience associated pruritus or pain. The cause of FD is unknown; it is speculated that the disease reflects an abnormal response to bacteria, particularly Staphylococcus aureus. Systemic antibiotic therapy is the mainstay of treatment.

The clinical features, diagnosis, and management of FD will be reviewed here. Other cicatricial alopecias are reviewed separately. FD is distinct from keratosis follicularis spinulosa decalvans, a rare genetic disorder characterized by keratotic follicular papules and cicatricial alopecia. (See "Evaluation and diagnosis of hair loss", section on 'Cicatricial alopecia'.)

CLASSIFICATION — FD is classified as a primary cicatricial alopecia, a group of disorders in which an inflammatory process targets the hair follicle, resulting in follicular destruction and permanent hair loss. This is in contrast to secondary cicatricial alopecia, in which scarring processes in the skin incidentally destroy hair follicles.

FD was further classified as a primary neutrophilic cicatricial alopecia in a classification scheme created by the participants of a 2001 workshop on cicatricial alopecia sponsored by the North American Hair Research Society [1]. This classification system was based upon the type of inflammatory infiltrate associated with specific subtypes of cicatricial alopecia. The classification of cicatricial and noncicatricial alopecias is reviewed in detail separately. (See "Evaluation and diagnosis of hair loss", section on 'Classification'.)

EPIDEMIOLOGY — It is generally accepted that FD is a rare disease; however, data on the epidemiology of FD are limited. One of the largest studies, a multicenter, retrospective study that incorporated data from patients evaluated in specialist hair clinics in Europe, America, Africa, and Australia, found that FD accounted for 3 percent of 3133 diagnoses of alopecia and 11 percent of 840 diagnoses of cicatricial alopecia [2].

Most case series demonstrate a male predominance, with male-to-female ratios ranging from 1.3:1 to 6.5:1 [3-9]. Most patients (73 percent) in the multicenter, retrospective study described above were female [2]. Classic FD has not been reported in children. However, tufted folliculitis, a condition that may be a clinical variant of FD or a distinct entity, has been reported in a 10-year-old child [10]. (See 'Clinical features' below.)

PATHOGENESIS — The cause of FD is unknown. Although S. aureus is frequently found in cultures taken from pustules from sites of FD, FD is not considered to be a simple bacterial infection. One major theory for the pathogenesis of FD is the concept that FD is caused by staphylococcal superantigens that bind to class II major histocompatability complex (MHC) proteins, causing nonspecific activation of T lymphocytes, resulting in release of cytokines and follicular destruction [11]. However, staphylococcal superantigens may not be present in a subset of patients [12].

A role for a defect in the epidermal barrier has also been proposed based upon a study that found S. aureus colonization in nonlesional and subepidermal skin in 16 of 20 patients with FD and S. aureus on lesional skin [12]. A subepidermal reservoir of pathogenic flora could contribute to the chronicity of FD.  

Other proposed contributors to the development of FD include defects in cell-mediated immunity or leukocyte function (eg, a defect that results in intracellular persistence of organisms after phagocytosis) [13,14], an autoimmune process [13], a genetically determined immune deficiency [7], pathogenic biofilms [15], and a congenital abnormality of follicular orifices [16]. In support of a role for genetic susceptibility in a subset of patients with FD, several familial cases have been reported [17-19].

The immunologic events that may contribute to FD were investigated in a study in which biopsy specimens from newly diagnosed patients with FD and other scalp disorders were evaluated with immunohistochemical stains [4]. The major findings of this study included that CD4+ T cells outnumbered CD8+ T cells in the inflammatory infiltrate in FD, cytokine expression patterns suggested both Th1- and Th2-mediated immune responses in FD, interleukin (IL) 8 and intercellular adhesion molecule (ICAM)-1 expression in the follicular epithelium may contribute to neutrophil recruitment in FD, and fibrogenic cytokines, such as fibroblast growth factor (FGF)-beta and transforming growth factor (TGF)-beta, may play a role in FD-related scarring. Unexpectedly, the study also found only weak to moderate expression of IL-1-beta and tumor necrosis factor (TNF)-alpha, cytokines strongly associated with superantigen stimulation, in specimens from sites of FD. Additional research is necessary to clarify the pathogenic mechanisms that lead to the development of FD.

CLINICAL FEATURES — The key clinical features of active FD are (picture 1A-B):

●One or more confluent areas of scarring alopecia on the scalp

●Multiple pustules (with or without inflammatory papules) on the scalp, particularly at the periphery of areas of alopecia

FD may involve any area of the scalp, and multifocal involvement on the scalp is common [3,14]. While there are case reports of FD in places other than the scalp, such as the beard, face, and nape of the neck, this is uncommon [3,20,21].

The patches of alopecia exhibit the smooth surface and absent follicular orifices that are characteristic signs of cicatricial alopecia. This contrasts with noncicatricial alopecia, in which the follicular orifices are characteristically preserved. The patches of alopecia gradually enlarge as the disease progresses.

In addition to crops of pustules and inflammatory papules at the periphery of areas of alopecia [13], tufted hairs (4 to 20 hair shafts emerging from a single follicular orifice) also may be present, a feature referred to as "tufted folliculitis" (picture 2A-B). Tufted folliculitis is not exclusive to FD and may be seen in other forms of cicatricial alopecia [13,22]. There is disagreement about whether patients in whom tufted folliculitis is the predominating feature have a clinical variant of FD or whether tufted folliculitis is a distinct disease [5,6,13,23,24].

Perifollicular scale extending onto the hair shaft may be visible in patients with FD. Tunneling of hair shafts beneath the skin surface is an additional feature that may be present (picture 2C). Perifollicular scale may be seen in other forms of lymphocytic or neutrophilic cicatricial alopecia. In contrast, tunneling of hair shafts typically is limited to neutrophilic cicatricial alopecia.

The clinical findings of FD may be asymptomatic or accompanied by pruritus or pain. Purulent discharge and spontaneous bleeding from affected areas are additional bothersome symptoms that may be present.

The appearance of quiescent or partially treated FD differs from active disease (picture 2C). These patients lack pustules and may present only with scarring alopecia and perifollicular erythema or scale. At this stage, clinical distinction between FD and primary lymphocytic cicatricial alopecias can be difficult. This has been described as the "folliculitis decalvans-lichen planopilaris phenotypic spectrum" [25,26].

HISTOPATHOLOGY — The biopsy findings of FD are variable and change with disease activity. There are no pathognomonic findings.

The major histologic feature of early, active disease is follicular-based neutrophilic pustules, often with surrounding acute and chronic inflammation. Foreign body giant cells may be present, reflecting a reaction to follicular damage and the release of follicular contents into the dermis [27]. The inflammatory infiltrate may extend from the perifollicular area into the interfollicular dermis. Inflammation usually is most prominent in the superficial dermis and mid-dermis and tends not to extend into the subcutaneous tissue. Consistent with the scarring nature of FD, fibrosis also may be detected.

Chronic inflammation is more prominent in long-standing disease; plasma cells are often present, and only a few neutrophils may be detected. As a result, this stage of disease can be difficult to distinguish histologically from lymphocytic cicatricial alopecia. Late-state lesions may exhibit diffuse dermal scarring.

The histologic findings of FD differ from dissecting cellulitis of the scalp, a neutrophilic cicatricial alopecia that is characterized by deep-seated, cystic nodules that merge to form sinus tracts. The extension of inflammation into the deep dermis and subcutaneous tissue in dissecting cellulitis of the scalp contrasts with the more superficial inflammation that typically is detected in FD [28]. (See 'Differential diagnosis' below.)

DIAGNOSIS — The only findings required for a diagnosis of FD are scarring hair loss and current or prior clinical or histologic evidence of a neutrophilic inflammatory infiltrate (ie, pustules or histologic findings). Once this is identified, further review of the clinical and histologic features is indicated to confirm the diagnosis because of overlap with other forms of alopecia. A diagnosis of FD is made when the sum of the clinical and histologic findings are determined to be more consistent with FD than other forms of alopecia. No blood tests or radiologic studies are useful for the diagnosis of FD. A fungal culture to exclude tinea capitis may be helpful in certain clinical situations. (See 'Differential diagnosis' below.)

Physical examination — The physical examination should include a careful examination of the scalp. The following clinical findings offer support for a diagnosis of FD:

●One or more confluent areas of scarring alopecia on the scalp

●Absence of follicular ostia in areas of alopecia (a finding consistent with cicatricial alopecia)

●Pustules (with or without accompanying inflammatory papules), particularly at the periphery of areas of alopecia

●Perifollicular scale extending onto the hair shaft

●Tufting of hair shafts

The presence of all of the features above is not required for a diagnosis of FD. In particular, when disease is quiescent, pustules and inflammatory papules can be absent. Additionally, perifollicular scale and tufting of hair shafts are common, but not uniformly present, in FD [6,29].

Certain physical findings support alternative diagnoses in patients with pustular, scarring eruptions on the scalp. As an example, patients who also exhibit fluctuant nodules and abscesses should be evaluated for dissecting cellulitis of the scalp. In addition, the possibility of acne keloidalis nuchae should be considered when a pustular scalp eruption is accompanied by firm, dome-shaped papules and involvement is primarily limited to the occipital scalp. (See 'Differential diagnosis' below and "Evaluation and diagnosis of hair loss", section on 'Physical examination' and "Evaluation and diagnosis of hair loss", section on 'Cicatricial alopecia' and "Dissecting cellulitis of the scalp" and "Acne keloidalis nuchae: Pathogenesis, clinical manifestations, and diagnosis".)

Examination of the rest of the skin should be performed as part of the initial evaluation. This enables the recognition of involvement in areas other than the scalp and may aid in the identification of features that support a different form of alopecia.

Dermoscopy — Dermoscopy (trichoscopy) can be useful for visualization of the absence of follicular ostia in cicatricial alopecia. Additional reported common findings of dermoscopic examination of FD include tufted hairs; perifollicular erythema; tubular, perifollicular scale; "perifollicular epidermal hyperplasia in a starburst pattern" (a conical elevation of the epidermis at the base of tufted hairs); cicatricial, white patches; hair diameter diversity; and large, follicular pustules with an emerging hair shaft [29,30].

Biopsy — For patients with pustules (a clinical finding consistent with a neutrophilic inflammatory infiltrate), the most important goal of the biopsy is to confirm the presence of a scarring process. In contrast, for patients in whom scarring alopecia is clearly evident on physical examination but pustules are absent, the goal of biopsy is to evaluate the inflammatory infiltrate to distinguish FD from lymphocytic cicatricial alopecias. Performing a biopsy that includes tissue demonstrating both clinical signs of scarring (eg, smooth, shiny area devoid of hair and follicular ostia) and active inflammation (eg, pustules, erythema, scale, or crust) allows for evaluation for both of these important features. The ideal site for the biopsy often is the periphery of patch of alopecia.

A 4 mm punch biopsy that extends into the subcutaneous fat is our preferred procedure for pathologic evaluation of FD. Dermatopathologists differ on the number of biopsies that should be performed in patients with alopecia [31,32]. Although some dermatopathologists prefer to receive two biopsies when evaluating alopecia to allow for examination of tissue in both vertical and horizontal sections, we find that a single biopsy specimen sectioned horizontally usually is sufficient to identify histologic findings consistent with FD.

It is important to indicate on the requisition form that the specimen is for the evaluation of alopecia, since some laboratories will process the tissue differently than a standard skin biopsy. In addition, because other cicatricial alopecias can exhibit overlapping histopathologic features, it is helpful to give a brief description of the clinical findings, including morphology, distribution, and duration.

DIFFERENTIAL DIAGNOSIS — The differential diagnosis for FD is broad and can vary with the clinical features present at the time of evaluation. Although the sight of pustules often first brings to mind superficial bacterial folliculitis, a very common condition on hair-bearing skin that is most often caused by S. aureus, scarring alopecia is not a feature of superficial bacterial folliculitis.

When scarring and many pustules are present, the differential diagnosis focuses on other primary cicatricial alopecias that present with pustules, including dissecting cellulitis of the scalp, acne keloidalis nuchae, and erosive pustular dermatosis of the scalp. Attention to the clinical features usually easily distinguishes FD from these diagnoses. Tinea capitis, an occasionally pustular fungal infection that may result in secondary alopecia, also should be included in the differential diagnosis:

●Dissecting cellulitis of the scalp – Dissecting cellulitis of the scalp is an uncommon primary neutrophilic cicatricial alopecia that may occur alone or in conjunction with acne conglobata and hidradenitis suppurativa as part of the "follicular occlusion triad" (or "tetrad" if pilonidal sinus is included). Young Black men are the most common population affected. Patients with dissecting cellulitis of the scalp develop follicular papules, pustules, fluctuant nodules, and abscesses on the scalp that lead to scarring (picture 3A-B). Fluctuant nodules and abscesses are not features of FD. (See "Dissecting cellulitis of the scalp".)

●Acne keloidalis nuchae – Acne keloidalis nuchae is a relatively common primary cicatricial alopecia that most frequently occurs in Black men. Key clinical features include dome-shaped, firm, follicular papules and pustules on the occipital scalp (picture 4). Keloidal plaques may also develop. The restriction of involvement to the occipital scalp and the development of firm papules and keloidal plaques distinguish acne keloidalis from FD. (See "Acne keloidalis nuchae: Pathogenesis, clinical manifestations, and diagnosis".)

●Erosive pustular dermatosis of the scalp – Erosive pustular dermatosis of the scalp is a rare, primary, mixed cicatricial alopecia that primarily occurs in older adult individuals. The disorder often follows trauma or surgery on the scalp. Key clinical features are sterile pustules, erosions, and crusted plaques that lead to scarring (picture 5). (See "Erosive pustular dermatosis of the scalp".)

●Tinea capitis – Inflammatory tinea capitis is an infection caused by dermatophytes that can mimic the appearance of FD [33,34]. Key clinical features of inflammatory tinea capitis include erythematous plaques, crusting, drainage, and sometimes pustules (picture 6). Cervical lymphadenopathy typically is present. Tinea capitis can be differentiated from FD with a potassium hydroxide preparation, fungal culture, or biopsy. (See "Tinea capitis".)

In addition to the disorders above, the possibility of cicatricial alopecia secondary to erlotinib should be considered in patients who develop pustules and cicatricial alopecia during erlotinib treatment. Case reports have documented the occurrence of erlotinib-induced cicatricial alopecia [35,36].

A greater challenge for the clinical diagnosis of FD arises in patients who present with scarring alopecia and few or no pustules. The differential diagnosis includes FD and several primary lymphocytic cicatricial alopecias, including lichen planopilaris, discoid lupus erythematosus, and central centrifugal cicatricial alopecia. In such cases, close attention for subtle clinical features and a biopsy are valuable tools for diagnosis:

●Lichen planopilaris – Key clinical features of lichen planopilaris are perifollicular erythema, perifollicular scale, and multiple smooth patches of scarring alopecia (picture 7). Common histologic findings are lymphocytes and fibrosis around hair follicles, with thinning of the follicular epithelium, a lichenoid interface dermatitis, and eventual follicular destruction [14]. While there may be occasional plasma cells in lichen planopilaris, the presence of neutrophils and/or large amounts of plasma cells favors FD. (See "Lichen planopilaris".)

●Discoid lupus erythematosus – Key clinical features of discoid lupus erythematosus on the scalp are erythematous, scaly plaques that evolve to patches of scarring alopecia that often exhibit depigmentation, peripheral scale, and follicular plugging (picture 8). There may be concomitant involvement of other sites on the head and neck (particularly the conchal bowls of the ears) or other sun-exposed skin. A biopsy reveals characteristic changes of lupus at both the dermal-epidermal junction and the follicular epithelium, consisting of hyperkeratosis, atrophy, vacuolar change at the dermal-epidermal junction, and a superficial and deep perivascular lymphocytic infiltrate [14]. Neutrophils are present only rarely. (See "Overview of cutaneous lupus erythematosus", section on 'Discoid lupus erythematosus'.)

●Central centrifugal cicatricial alopecia – Key clinical features of central centrifugal cicatricial alopecia are scarring alopecia that begins on the crown of the scalp and expands centrifugally (picture 9). The disorder is most common in women of African descent. Pruritus may or may not be present. Scale and erythema are usually absent. Occasionally, pustules are present, which may contribute to confusion with FD. In active disease, biopsy reveals a perifollicular lymphocytic infiltrate surrounding the upper follicle [14]. Premature desquamation of the inner root sheath may also be detected. (See "Central centrifugal cicatricial alopecia".)

TREATMENT — All patients with active FD should be treated because the disease destroys hair follicles and causes permanent hair loss. Successful treatment reduces symptoms, halts the inflammatory process, and prevents additional hair loss (picture 10). However, no randomized trials have evaluated therapies for FD, and most information on treatment efficacy is derived from retrospective studies, case series, case reports, and other documentation of clinical experience [37].

Whom to treat — Treatment is most beneficial for patients with active disease. Active FD is suggested by pustules, crusts, erythema, symptoms of pruritus or pain, progressive scarring, or progressive hair loss. Patients with end-stage FD, in which signs of active disease are absent, are unlikely to benefit from treatment.

Pretreatment counseling — Providing patients with realistic expectations is an important part of patient management. We inform all patients of the variable response to treatment and the potential for relapse. In addition, we explain that although successful treatment can prevent further hair loss, regrowth of hair from sites where FD has destroyed hair follicles will not occur (picture 10).

Pretreatment culture — Bacterial cultures of pustules and sensitivity testing should be performed for all patients who present with findings consistent with FD because treatment decisions are made based upon the culture and sensitivity results. Case series suggest that bacterial cultures grow S. aureus in well over 50 percent of patients [3,4,6,7].

Initial treatment — The severity of disease influences the approach to treatment. Oral antibiotic therapy is the mainstay of treatment; patients with severe inflammation (eg, extensive pustulation, extensive erythema, and severe pain or pruritus (picture 1A)) may also benefit from systemic glucocorticoid therapy. (See 'General approach' below and 'Severe inflammation' below.)

General approach — Our first-line treatment is typically a tetracycline-class oral antibiotic, provided antibiotic cultures demonstrate susceptibility to tetracyclines. Tetracyclines are also our preferred initial treatments for patients with culture-negative FD. Adjunctive local corticosteroid therapy may be helpful for further suppression of inflammation and improvement of residual symptoms. (See 'Single oral antibiotic' below and 'Intralesional or topical corticosteroid therapy' below.)

Our clinical experience suggests that topical antibiotics alone may be sufficient in select patients with very limited disease; however, most patients require systemic therapy to achieve control of FD. (See 'Topical antibiotics' below.)

Single oral antibiotic — Oral antibiotic therapy guided by the results of culture and antibiotic susceptibility testing can be effective for reducing symptoms and clearing active lesions [5,14,38]. However, the long-term response to treatment is unpredictable; rapid relapse often occurs after discontinuation [3,14]:

●Selection – A variety of antistaphylococcal and broad-spectrum oral antibiotics have been used for treatment. Tetracyclines are our first choice for patients with culture results that demonstrate bacterial susceptibility to tetracyclines and patients with negative cultures because of their anti-inflammatory properties and tolerability.

However, evidence on antibiotic therapy is limited and insufficient to conclude that tetracyclines are more effective than other antibiotics. Examples of other oral antibiotics that may be helpful based upon clinical experience of experts include cephalosporins, ciprofloxacin, trimethoprim-sulfamethoxazole, and erythromycin [5,13,17,38].

●Administration – When treating adults with antibiotics, our initial course of treatment varies in duration, depending on disease activity and the response to treatment. Our standard dose for tetracyclines for adults is 50 to 100 mg of doxycycline or minocycline given twice daily. Symptoms often improve within one to two months.

In patients who respond to antibiotic therapy within one to two months, the medication can be tapered or discontinued after approximately three months of treatment, with the knowledge that the disease often recurs. If symptoms recur, we reinitiate treatment. Once the disease is under control, we taper the antibiotic to the lowest dose that maintains remission.

Patients who do not respond within one to two months may be given longer courses of antibiotic treatment provided signs of progressive improvement are evident. If a patient fails to respond to oral antibiotic therapy and repeat culture and susceptibility testing does not demonstrate a reason for resistance, we proceed to second-line therapy. (See 'Failure of initial treatment' below.)

●Efficacy – Efficacy of tetracyclines is supported by retrospective studies [39,40]. As an example, in a review of 60 patients with FD that included 36 patients treated with doxycycline or minocycline, 91 percent achieved a response (>75 percent improvement in symptoms and inflammatory signs and no increase in the size of the largest alopecic patch) [39]. In addition, a case series documents clearance of scalp lesions in several patients treated with minocycline monotherapy (100 mg twice daily for one to three months) [8].

Intralesional or topical corticosteroid therapy — We use intralesional or topical corticosteroid therapy on an as needed basis to aid in calming symptoms of localized inflammation (eg, itching, pain) that persist despite oral antibiotic therapy. Data to guide use of these therapies are lacking. Patient and clinician preference influences the selection between intralesional and topical therapy.

The best regimen for local corticosteroid therapy is not established. For intralesional injection, we use a concentration of 10 mg/mL of triamcinolone acetonide for injections in the affected area. We inject approximately 0.1 mL into each injection site, with individual injections separated by approximately 1 cm. We seldom exceed a dose of 20 mg of triamcinolone acetonide per treatment session. Treatment sessions should be separated by four to six weeks or longer. The pain experienced during injection is a disadvantage of intralesional therapy. (See "Intralesional corticosteroid injection".)

Topical therapy typically involves use of a high-potency topical corticosteroid (group 1 or group 2 (table 1)). The topical corticosteroid can be applied as needed to maintain improvement, with the goal of tapering to the lowest frequency that maintains improvement. For example, initially, the topical corticosteroid can be applied once or twice daily for two to four weeks, followed by application two days per week, and then subsequently tapered as tolerated.

Side effects associated with local corticosteroid therapy are reviewed separately. (See "Intralesional corticosteroid injection", section on 'Adverse effects and pitfalls' and "Topical corticosteroids: Use and adverse effects", section on 'Adverse effects'.)

Topical antibiotics — No studies have evaluated the efficacy of topical antibiotic monotherapy. However, our experience with topical clindamycin in a few patients with very mild FD (few active lesions and limited, fairly stable, nondisfiguring scarring) suggests that some patients can achieve disease control with topical therapy alone. We generally restrict topical antibiotic therapy to patients with mild FD who desire to avoid systemic antibiotic therapy. As with patients treated with oral antibiotics, cultures and antibiotic susceptibility testing should guide the selection of a topical agent.

It is unclear whether combining topical and oral antibiotic therapy is more effective than oral therapy alone; we do not typically use topical and oral antibiotics simultaneously.

Severe inflammation — The small subset of patients who present with severe inflammation (eg, extensive pustulation, marked erythema, and severe pain or pruritus) warrant measures to rapidly improve symptoms. In conjunction with antibiotic therapy, systemic glucocorticoids can help improve signs and symptoms of severe inflammation.

Antibiotics — Our initial approach to antibiotic therapy is similar to patients with less severe disease, involving treatment with a single oral antibiotic selected based upon the results of culture and susceptibility testing. Patients who do not respond sufficiently are candidates for combination therapy with rifampin and clindamycin. However, use of rifampin and clindamycin as first-line treatment for severe disease has been advocated by some authors [39]. (See 'Failure of initial treatment' below and 'Rifampin and clindamycin' below.)

Systemic glucocorticoids — Systemic glucocorticoids are occasionally used for severe FD because they can calm inflammation during flares. However, long-term systemic glucocorticoid therapy is not recommended because of the side effects associated with this form of therapy [14,17]. (See "Major adverse effects of systemic glucocorticoids".)

There are no guidelines for the dosing of systemic glucocorticoids in the treatment of FD. On the rare occasions we use this treatment, we prescribe a short course of prednisone (1 mg/kg tapered to discontinuation over two to three weeks) in an attempt to attain disease control while awaiting the onset of action of antibiotic therapy.

Failure of initial treatment — A more aggressive approach to treatment is warranted for patients who do not achieve a satisfactory response to single oral antibiotic therapy. Our treatment regimen of choice for these patients is rifampin and clindamycin. Oral isotretinoin is another alternative for patients with insufficient responses to single oral antibiotic therapy.

Rifampin and clindamycin — Both rifampin and clindamycin have activity against S. aureus, are lipid soluble, and kill intracytoplasmic organisms, making them highly efficacious antibacterial agents. The potential side effects of this regimen make it a less favorable choice for first-line therapy:

●Administration – We treat adults with 300 mg of rifampin and 300 mg of clindamycin, both given twice daily for an initial course of 10 weeks. Rifampin should always be given in combination with another antibiotic because there is rapid emergence of resistance to rifampin when the drug is given as monotherapy. Some authors suggest that ciprofloxacin or clarithromycin can be used as alternatives to clindamycin therapy [6].

Adverse effects of rifampin include staining of body secretions, liver function abnormalities, hemolytic anemia, thrombocytopenia, influenza-like syndromes, and drug interactions. Pseudomembranous colitis is a potential side effect of oral clindamycin treatment. (See "Rifamycins (rifampin, rifabutin, rifapentine)", section on 'Adverse effects' and "Clindamycin: An overview", section on 'Toxicity'.)

●Efficacy – Support for the use of rifampin and clindamycin in FD stems from case series and retrospective studies documenting successful treatment with this regimen [6,39,40]. In one series, 18 patients who had experienced recurrences of FD during or after treatment with systemic antibiotics selected based upon culture results received combination therapy with rifampin (300 mg twice daily) and clindamycin (300 mg twice daily). After one 10-week course of rifampin and clindamycin, 10 of 18 patients were clear of disease and did not experience a recurrence during follow-up of 2 to 22 months. An additional five patients improved but required extension to a 20-week or 30-week course of treatment. In a separate review of 60 patients with FD in which 21 received a similar regimen of clindamycin and rifampin for refractory FD, 91 percent achieved a response (>75 percent improvement in symptoms and inflammatory signs and no increase in the size of the largest alopecic patch) [39]. Other series have documented both remissions and relapses after rifampin and clindamycin therapy [3,9].

Oral isotretinoin — Oral isotretinoin is a retinoid that is postulated to improve FD through immunomodulatory effects [41]. Disadvantages of isotretinoin are its teratogenicity and broad side effect profile. We generally reserve isotretinoin for patients who fail or cannot receive clindamycin and rifampin therapy:

●Administration – The optimal regimen for isotretinoin therapy is unknown. Available data suggest that doses between 0.1 and 1 mg/kg per day given for one to eight months may be sufficient [41,42]. One retrospective study found a nonstatistically significant trend towards reduced risk for relapse with doses of at least 0.4 mg/kg per day given for at least three months [42]. Frequent reassessment during treatment is helpful for guiding dosing and the appropriate duration of treatment. Signs of improvement may be evident within the first one to two months [42].

Because of the teratogenic effects of isotretinoin, participation in the iPLEDGE program, a risk management program designed to reduce risk for fetal exposure to isotretinoin, is required to prescribe the drug in the United States. Examples of other side effects of oral isotretinoin include cheilitis, xerosis, hypertriglyceridemia, and visual changes. The side effects of isotretinoin are reviewed in greater detail separately. (See "Oral isotretinoin therapy for acne vulgaris", section on 'Adverse effects'.)

●Efficacy – Limited data suggest that isotretinoin can be beneficial for FD in some patients. Support for the efficacy of isotretinoin arises from retrospective studies. In a review of 28 patients with clinical or histologically confirmed diagnoses of FD, 9 of 10 patients treated with isotretinoin (0.2 to 0.5 mg/kg per day for five to seven months) alone or in combination with other therapies experienced stable remissions with treatment, defined as residual erythema but no pustules and only a few crusts [41]. Six of these patients were able to discontinue treatment completely and remained in complete remission during follow-up periods ranging from four months to two years. Two needed continued intermittent dosing several times a week to sustain remission. Another retrospective study of 39 males treated with 0.1 to 1 mg/kg per day of isotretinoin for a median of 2.5 months (range of one to eight months) found complete responses (absence of active lesions) in 32 patients (82 percent) and partial responses (persistence of some active pustules or crusts) in 4 patients (10 percent). Of the responders, a telephone interview performed between 0.5 years and 7 years after treatment revealed relapses of disease in 20 patients (56 percent) with a median time to relapse of 2.5 months [42].

Additional authors have reported benefit in patients treated with regimens containing isotretinoin [3,43], including a case report documenting successful treatment of FD with combination treatment with oral isotretinoin, oral clindamycin, and oral prednisolone [43]. However, other authors report poor results with isotretinoin therapy [44-46].

Alternative therapies — Limited data suggest that several other therapies may be useful for achieving clinical improvement in FD [37]. Additional studies are necessary to confirm the efficacy of these treatments:

●Antimicrobial cleansers – Topical antimicrobial cleansers, such as products containing povidone-iodine or triclosan [17], have been proposed by some authors as helpful adjunctive therapies. We do not routinely use topical antimicrobial cleansers in the management of our patients.

●Topical tacrolimus – Topical tacrolimus 0.1% ointment was associated with improvement of FD in four patients, including three who had failed other therapies [47].

●Fusidic acid – Treatment regimens containing fusidic acid have yielded mixed results [9,14,19,48,49]. A potential beneficial effect was demonstrated in a report of three patients treated with oral fusidic acid (1500 mg per day for three weeks), oral zinc sulfate (400 mg per day for six months), and topical fusidic acid cream (applied for two weeks) followed by maintenance treatment with zinc sulfate (200 mg per day) [49]. Treatment was associated with remissions that lasted at least one year. Fusidic acid is not commercially available in the United States.

●Dapsone – There are few data on the effects of dapsone, an antimicrobial agent with inhibitory effects on neutrophils, on FD. In two patients, dapsone (75 or 100 mg per day for four to six months) followed by maintenance treatment with 25 mg of dapsone daily was associated with disease remission persisting for at least one year [50]. However, relapse occurred after withdrawal of therapy.

●Tumor necrosis factor (TNF)-alpha inhibitors – Treatment with the TNF-alpha inhibitors infliximab and adalimumab have been associated with improvement in individual patients with refractory disease [44,51].

●Intravenous immune globulin (IVIG) – A case report documents improvement in FD after treatment with IVIG [52].

●Procedural therapy – A few reports document improvement in FD following procedural therapies. Occasional patients with severe, refractory FD that has not responded to medical therapy have achieved improvement with procedures that destroy the hair follicle, including neodymium-doped yttrium aluminum garnet (Nd:YAG) laser [53,54] and radiation therapy [55]. Photodynamic therapy (PDT) using a red light source (630 nm) has been associated with improvement in FD in a small prospective study and case series; however, the benefit of PDT has been questioned and treatment results vary [39,45,56-58]. A remission of FD upon shaving of scalp hair was reported in one patient [46].

COSMETIC MEASURES — The chronic inflammation and hair loss of FD can cause significant disfigurement. Patients with FD often spend a significant amount of time and effort hiding or covering their hair loss.

Camouflage — Examples of products that may be useful for minimizing the appearance of hair loss include scalp camouflaging agents (eg, topical hair fibers, powder cakes, lotions, sprays, scalp tattooing), wigs, hairpieces, and hair extensions [59]. Hair styling techniques can also reduce the visibility of alopecia.

Hair transplantation — Hair restoration surgery is an option for patients with permanent hair loss from FD. Because of concern for a resurgence of active disease in transplanted areas, we reserve hair transplantation for patients who exhibit no disease activity for several years without treatment [17]. Of note, the initial development of FD in an area of grafted hairs has been reported 20 years after hair transplant surgery in a patient who underwent hair transplantation for male pattern hair loss [60].

PROGNOSIS — FD may remain localized to a particular area of the scalp or may progress to widespread scalp involvement over the course of months to years. FD does not affect other organ systems and is not life threatening. Onset of disease before 25 years of age and long duration of disease are associated with greater disease severity [39].

Early treatment is essential to limit hair loss. The course of FD following successful treatment is variable. Patients may experience long-term remissions or rapid recurrences of disease. A retrospective study on course and treatment outcome of 23 patients with FD after 3 months to 12 years of follow-up found that after treatment, 39 percent of patients achieved remission off of medication, 48 percent required continued treatment for disease control, and 13 percent were uncontrolled despite treatment [38].

The development of squamous cell carcinoma (SCC) in FD has been reported [61]. However, the patient also had a history of extensive sun exposure, and it is unclear whether FD or ultraviolet light exposure contributed to the development of SCC.

PATIENT AND CLINICIAN SUPPORT — FD can negatively affect patients' quality of life [39,62]. A helpful resource for patients and clinicians is the Scarring Alopecia Foundation, which offers a website with information and links to local support groups and international conferences.

SUMMARY AND RECOMMENDATIONS

●Classification – Folliculitis decalvans (FD) is an uncommon, chronic cause of hair loss that is characterized by follicular pustules and scarring alopecia. FD is classified as a primary neutrophilic cicatricial alopecia. (See 'Classification' above.)

●Epidemiology – FD usually occurs in adults. The disorder is more common in men than in women. (See 'Epidemiology' above.)

●Pathogenesis – The pathogenesis of FD is not well understood. Although Staphylococcus aureus is often found in cultures taken from sites of FD, the disorder does not appear to be simply a chronic bacterial infection. One theory suggests that an immunologic response to staphylococcal superantigens may play a role in FD. (See 'Pathogenesis' above.)

●Clinical features and diagnosis – The key clinical features of active FD are:

•One or more confluent areas of scarring alopecia on the scalp

•Multiple pustules (with or without inflammatory papules) on the scalp, particularly at the periphery of areas of alopecia (picture 1A-B)

Other physical findings of active disease include inflamed or crusted, follicular papules, tufted hairs, and tunneling of hair shafts beneath the skin surface (picture 2A, 2C). Patients with quiescent or partially treated FD may lack pustules and may exhibit only scarring alopecia and perifollicular erythema or scale, a presentation that may be difficult to distinguish from other cicatricial alopecias. The diagnosis of FD is confirmed by correlation of the clinical and histologic findings. (See 'Clinical features' above and 'Diagnosis' above.)

●Treatment – Data are limited on the efficacy of treatments for FD. Antibiotic therapy is the mainstay of treatment. Successful treatment consists of reduction in symptoms, arrest of the inflammatory process, and prevention of further hair loss (picture 10) (see 'Treatment' above):

•Pretreatment culture – Bacterial cultures should always be performed in patients with FD because the results aid in treatment selection. (See 'Pretreatment culture' above.)

•Initial treatment – For patients with FD, we suggest that an oral antibiotic selected based upon culture and antibiotic susceptibility testing should be used as initial therapy (Grade 2C). We usually use doxycycline or minocycline and give an initial course of treatment that lasts two to three months. We treat patients with negative cultures similarly. (See 'Initial treatment' above.)

•Failure of initial treatment – For patients who fail to respond adequately to conventional oral antibiotic therapy, we suggest a trial of rifampin and clindamycin as second-line therapy (Grade 2C). Patients treated with this regimen should be followed for treatment-related side effects. Rifampin should not be given alone because of a high risk for the development of antibiotic resistance. Oral isotretinoin is an alternative therapy for patients who fail or who cannot receive clindamycin and rifampin therapy. (See 'Failure of initial treatment' above.)