Acta Clin Croat 2011; 50:395-402 Review DIFFERENTIAL DIAGNOSIS OF THE SCALP HAIR FOLLICULITIS Liborija Lugović-Mihić1, Freja Barišić2, Vedrana Bulat1, Marija Buljan1, Mirna Šitum1, Lada Bradić1 and Josip Mihić3 1University Department of Dermatovenereology, 2University Department of Ophthalmology, Sestre milosrdnice University Hospital Center, Zagreb; 3Department of Neurosurgery, Dr Josip Benčević General Hospital, Slavonski Brod, Croatia SUMMARY – Scalp hair folliculitis is a relatively common condition in dermatological practice and a major diagnostic and therapeutic challenge due to the lack of exact guidelines. Generally, inflammatory diseases of the pilosebaceous follicle of the scalp most often manifest as folliculitis. There are numerous infective agents that may cause folliculitis, including bacteria, viruses and fungi, as well as many noninfective causes. Several noninfectious diseases may present as scalp hair folli- culitis, such as folliculitis decalvans capillitii, perifolliculitis capitis abscendens et suffodiens, erosive pustular dermatitis, lichen planopilaris, eosinophilic pustular folliculitis, etc. The classification of folliculitis is both confusing and controversial. There are many different forms of folliculitis and se- veral classifications. According to the considerable variability of histologic findings, there are three groups of folliculitis: infectious folliculitis, noninfectious folliculitis and perifolliculitis. The diagno- sis of folliculitis occasionally requires histologic confirmation and cannot be based solely on clinical appearance of scalp lesions. This article summarizes prominent variants of inflammatory diseases of the scalp hair follicle with differential diagnosis and appertaining histological features. Key words: Folliculitis; Scalp; Perifolliculitis Introduction Classification of folliculitis is both confusing and controversial. There are many different forms of fol- Folliculitis is defined as the presence of inflamma- liculitis and several classifications. According to the tory cells within the wall and ostia of the hair fol- considerable variability of histologic findings, there licle, creating a follicular-based pustule. Folliculitis are three groups of folliculitis: infectious folliculitis, frequently manifests on the scalp, face, neck and but- 1 noninfectious folliculitis and perifolliculitis (Table 1). tocks . It can be superficial (ostiofolliculitis) or deep The last one, perifolliculitis, is the process in which (such as furuncle, carbuncle, etc.). When folliculitis inflammatory cells surround the follicle without pen- lesions are deep, they are usually accompanied by peri- etrating into it. Histologically, there is a chronic peri- follicular inflammation, followed by follicular rupture follicular lymphocytic inflammation that clinically (perifolliculitis) and resulting abscess. manifests as the presence of prominent plugs of kera- tin within the dilated follicular orifice. Correspondence to: Liborija Lugović-Mihić, MD, PhD, Universi- Folliculitis is usually characterized by the pres- ty Department of Dermatovenereology, Sestre milosrdnice Uni- ence of perifollicular erythema, papules, pustules and versity Hospital Center, Vinogradska c. 29, HR-10000 Zagreb, Croatia vesicles that may be perforated by a hair in acute cases, E-mail: [email protected] while chronic-stage lesions present as follicular hyper- Received April 20, 2009, accepted October 15, 2011 keratosis with prominent plugs of keratin within the Acta Clin Croat, Vol. 50, No. 2, 2011 395 Liborija Lugović-Mihić et al. Differential diagnosis of the scalp hair folliculitis Table 1. Differential diagnosis of the scalp hair folliculitis according Camacho et al.2 FOLLICULITIS AND PERIFOLLICULITIS Infections/infestations Noninfectious (folliculitides) Perifolliculitis Other Superficial Deep Superficial Deep Predominantly possibilities Predominantly (generally (generally (generally (generally lymphocytic (spongiotic granulomatous suppurative) granulomatous) suppurative) granulomatous) folliculitis) Primary Secondary Fungi: Demodicosis Acne vulgaris Acne vulgaris Pruritic Keratosis Demo- Perioral Dermatophytes folliculitis of pilaris and dicosis dermatitis Pityrosporum Favus and Rosacea and perioral Lupoid pregnancy keratosis Vitamin C Candida kerion dermatitis rosacea spinulosa deficiency Acneiform Acne Fox-Fordyce eruption Bacteria Tinea barbae Eosinophilic conglobata disease Keratosis Vitamin A secondary to (Bockhart`s pustular folliculitis Keloidal acne pilaris deficiency syphilis impetigo) Majocchi`s of the neck Infundibulo- atrophicans Secondary trichophytic Toxic erythema folliculitis Due to syphilis granuloma of the newborn Perforating Lichen lithium folliculitis planopilaris Viruses: Furuncle Follicular mucinosis Herpes simplex Toxicoderma: Pityriasis zoster Carbuncle Mechanical and Halogens rubra pilaris Molluscum chemical traumas Lithium contagiosum Sycosis Toxicodermas: Pseudofolliculitis Acneiform Halogens syphilis Steroids Pseudofolliculitis follicular orifice1. Inflammatory diseases of the scalp Thus, folliculitis can be classified according to his- hair follicle frequently manifest as folliculitis, which tological features and/or presence of microbiological may lead to cicatricial or non-cicatricial alopecia, de- agents. There are several characteristic histopathologic pending on whether or not the perifollicular infiltrate patterns of hair scalp folliculitis2. In acute folliculitis, or the etiologic agent spares the hair follicle2,3. It is moderate neutrophil infiltrate can be seen infiltrating often difficult to make an adequate diagnosis of scalp follicular epithelium, with the formation of micro- or hair folliculitis and it usually requires considerable macro abscesses. Tissue necrosis may be discrete and time and effort to recognize and treat the disease. is usually limited to the follicular infundibulum and Besides the noninfectious causes, there are numer- the adjacent dermis, or it may be significant, affect- ous infective pathogens that may cause folliculitis, ing the entire pilosebaceous complex. In chronic fol- including bacteria, viruses and fungi. Diabetes mel- liculitis there is moderately dense lymphocytic infil- litus, hyperhidrosis, maceration, tight-fitting clothes, trate, usually a granulomatous infiltrate with a foreign particularly in obese people, inadequate use of topical body reaction around the keratin. The inflammation is corticosteroids and halogenated compounds, skin care nodular, poorly defined and composed of neutrophils, products and topical hydrocarbons, such as oils or tars lymphocytes, histiocytes, and giant cells. Plasmacytic (occupational exposure) may precipitate exacerbation chronic folliculitis predominantly occurs in facial fol- of folliculitis. In addition, immunocompromised pa- licles, such as perioral dermatitis, keloidal acne and tients, such as HIV/AIDS patients, may present with solid facial edema, folliculitis decalvans and carbun- various types of folliculitis. cle2,4. 396 Acta Clin Croat, Vol. 50, No. 3, 2011 Liborija Lugović-Mihić et al. Differential diagnosis of the scalp hair folliculitis Other histological forms of folliculitis are pre- covered by grayish scales. Hairs break at 4-6 mm and dominantly eosinophilic folliculitides and spongiotic if they are plucked and placed on a black surface, one folliculitides with characteristic features of infundib- can see the surrounding white ‘frosted sheath’ (spores ulofolliculitis. One distinct form is follicular mucino- of the mosaic ectothrix). Hairs fluorescence in Wood’s sis, which often histologically presents in spongiotic light and can therefore be easily identified2. folliculitis as keratinocytes get separated by mucin Trichophytic ringworm tinea of the scalp (black dots deposits, but dermal mucin deposits can also be found tinea) affects only several follicles and manifests with in lupus erythematosus and Fox-Fordyce disease. De- multiple small alopecic areas, which sometimes merge struction of the hair follicle can sometimes ensue, at into a larger polycyclic patch with the characteristic the ‘end-stage’ of folliculitis. Suppurative and granu- interior composed of healthy hair. The most specific lomatous folliculitis generally destroys the follicle sign is the presence of ‘black dots’, which is very fragile leading to cicatricial alopecia. The presence of keratin hair infested by endothrix parasite, broken at the level is important as well. Prominent plugs of keratin with- of infundibulum or slightly above. Dermatopatho- in the dilated follicular orifice lead to chronic-stage logical features of tinea tonsurans are chronic der- perifolliculitis. matitis with vasodilatation, lymphocytic perivascular infiltrates with occasional spongiosis. Special staining Folliculitis Due to Infective Agents may reveal the fungus in the corneal layer, ecto- or The majority of infectious folliculitides are caused endothrix arthrospores and Adamson’s fringe. by bacteria and fungi (such as Pityrosporum, Demodex, Kerion Celsi is an inflammatory tinea of the scalp, or other agents)5-7. These clinical variants of folliculitis generally caused by zoophilic, geophilic or anthropo- can be diagnosed by adequate sampling, swabs, KOH philic dermatophytes, accompanied by severe inflam- examination/or fungal cultures of expressed follicu- matory reaction. It starts as tinea tonsurans and soon lar content. Thereby, diagnosis of these skin changes becomes indurated and covered with squamous crusts includes identification of the infection,