Tinea capitis: Clinical features and diagnosis

INTRODUCTION — 

Tinea capitis is a fungal infection of the scalp that most often presents with pruritic, scaling areas of hair loss. Trichophyton and Microsporum species of dermatophyte fungi are the major causes of tinea capitis. The infection is often contracted from another human or an animal through direct contact.

Tinea capitis primarily occurs in children. The most common clinical findings are single or multiple scaly patches with alopecia and patches of alopecia with black dots at follicular orifices that represent broken hairs (picture 1A-F). Other presentations include widespread scaling with subtle hair loss; a boggy, edematous, painful plaque studded with pustules called a kerion (picture 2); and favus, which characteristically exhibits multiple cup-shaped, yellow crusts (scutula) (picture 1G).

The pathogenesis, clinical features, and diagnosis of tinea capitis will be reviewed here. The management of tinea capitis is reviewed separately.

●(See "Tinea capitis: Management".)

Other dermatophyte infections are also reviewed separately.

●(See "Dermatophyte (tinea) infections".)

●(See "Onychomycosis: Epidemiology, clinical features, and diagnosis".)

●(See "Onychomycosis: Management".)

●(See "Infectious folliculitis", section on 'Dermatophytic folliculitis'.)

EPIDEMIOLOGY — 

Tinea capitis is a common disorder, with prevalences that vary geographically and demographically. Children, particularly prepubertal children, are most likely to develop tinea capitis. Some studies have identified higher prevalences in male children than in female children [1-6]. However, other studies have not corroborated this finding [7]. Occasionally, adults develop tinea capitis [8-12].

ETIOLOGY — 

Tinea capitis is a dermatophyte infection. Dermatophytes are filamentous fungi in the genera Trichophyton, Microsporum, and Epidermophyton that infect keratinized tissue of skin, hair, or nails. Organisms in the Trichophyton and Microsporum genera generally cause tinea capitis [13]. Tinea capitis due to Epidermophyton species is rare [14].

Dermatophytes are divided into anthropophilic (human), zoophilic (animal), and geophilic (soil) fungi. Anthropophilic and zoophilic dermatophytes are the most common causes of tinea capitis. Examples of dermatophyte species associated with tinea capitis include:

●Anthropophilic

•Trichophyton tonsurans

•Trichophyton mentagrophytes var. interdigitale

•Trichophyton violaceum

•Trichophyton soudanense

•Trichophyton schoenleinii

•Microsporum audouinii

•Epidermophyton floccosum (rare)

•Trichophyton rubrum (rare)

●Zoophilic

•Microsporum canis

•Trichophyton verrucosum

•Trichophyton equinum

•Microsporum nanum

•Trichophyton species of Arthroderma benhamiae [15]

●Geophilic

•Microsporum gypseum

•Microsporum fulvum

The likelihood that a particular dermatophyte is the cause of tinea capitis varies geographically and evolves over time [13,16]. A systematic review that assessed studies published between 2015 and 2022 supported M. canis, T. violaceum, T. tonsurans, T. soudanense, and M. audouinii as the most common causative organisms [16]. The most common causative organisms identified in the studies varied among countries and, in some cases, among locations within a country.

In the systematic review, M. canis was the predominant causative organism in studies in Algeria, Argentina, Indonesia, China, Poland, and additional countries [16]. T. violaceum was the predominant organism in studies from India, Ethiopia, and Switzerland. T. tonsurans was the most common causative organism in studies from the United States, Canada, and France. T. tonsurans was also the most common dermatophyte species identified in a subsequent study that assessed over 7000 positive tinea capitis fungal culture results from a major commercial laboratory in the United States [17].

Whether Trichophyton indotineae, an emerging dermatophyte species often associated with resistance to antifungal therapy, will become a major contributor to tinea capitis is uncertain. In a study that utilized polymerase chain reaction (PCR) to identify the causative species in culture isolates from 94 patients with tinea capitis in Iran, T. indotineae was present in five patients (5 percent) [18]. (See "Dermatophyte (tinea) infections", section on 'Treatment failure'.)

PATHOGENESIS

●Acquisition of infection – Tinea capitis is acquired through contact of the scalp with the causative dermatophyte. Acquisition of the fungus may result from direct contact with an infected individual or animal or from contact with a contaminated object (eg, comb, brush, or hat).

Contact with asymptomatic carriers of causative organisms is an additional mode of transmission that may play an important role in recurrences of tinea capitis and tinea corporis [19]. (See "Tinea capitis: Management", section on 'Cohabitant and household measures' and "Tinea capitis: Management", section on 'Treatment failure'.)

Once the dermatophyte comes in contact with the stratum corneum on the scalp, the establishment of infection is mediated by a variety of factors. As an example, mannan glycoproteins in dermatophyte cell walls promote adherence of dermatophytes to keratin-containing host tissue [20]. In addition, production of proteolytic enzymes, such as keratinase, by the dermatophytes enables invasion of the cytokeratin-containing tissues of the skin and hair [20]. The infection progresses from the stratum corneum of the epidermis, extending down the follicle and to the hair. Biofilms can form, which may make therapy more difficult [21].

●Types of infection – Dermatophyte infection of the hair may present in three forms: endothrix infection, ectothrix infection, and favus.

In endothrix infections, arthroconidia (fungal spores) are found within the hair shaft on direct microscopic examination. Common examples include T. tonsurans, T. violaceum, and T. soudanense infections.

In ectothrix infections, arthroconidia primarily surround the outside of the hair shaft. Dermatophytes often associated with ectothrix infections include T. verrucosum, M. canis, M. audouinii, M. nanum, and M. gypseum.

Favus is a unique presentation in which hyphae and air spaces are found within hair shafts. Favus results from infection with T. schoenleinii (and rarely other dermatophytes). (See 'Potassium hydroxide preparation' below.)

●Host defense – The innate immune system likely plays a significant role in host defense against dermatophyte infection. An in vitro study evaluating the role of inflammasomes, components of the innate immune system, found evidence to suggest that the NLRP3 inflammasome plays an important role in host defense against M. canis infection [22].

The reasons for the predominance of tinea capitis in children are not well understood. Proposed theories to explain the infrequency in adults include effects related to the fungistatic properties of short- and medium-chain fatty acids in postpubertal sebum and the colonization of adults by commensal yeasts, such as Pityrosporum, that may inhibit infection with dermatophytes [23].

CLINICAL MANIFESTATIONS — 

Tinea capitis may present with a variety of clinical features. Pruritus is a common symptom in the various presentations of tinea capitis.

Clinical variants — There are five major clinical variants of tinea capitis as well as an asymptomatic carrier state. The most common clinical manifestations are scaly patches with alopecia and patches of alopecia with visible black dots. The causative organism and the host immune response to infection influence the clinical presentation.

●Scaly patches with alopecia – Single or multiple scaly patches with hair loss are a common presentation of ectothrix infections (eg, M. canis, T. verrucosum, M. audouinii, M. nanum, and M. gypseum) (picture 1A-C, 1E and picture 1D).

Individual patches are often a few centimeters to several centimeters in diameter. The patches enlarge centrifugally over the course of weeks to months. Erythema may be present.

●Patches of alopecia with black dots – Endothrix infections (eg, T. tonsurans, T. violaceum, and T. soudanense) may present with manifestations often referred to as "black dot tinea capitis." Multiple black dots, which represent the distal ends of hairs that have broken at the surface of the scalp, are present at follicular orifices within areas of alopecia (picture 1F).

The broken hairs are a result of weakening of the hair shaft secondary to the endothrix infection. The alopecic areas may be single or multiple and typically range from a few centimeters to several centimeters in diameter.

●Widespread scaling with subtle hair loss – Tinea capitis may exhibit diffuse scaling on the scalp without clear areas of alopecia (picture 3). This presentation may closely resemble seborrheic dermatitis and may be due to unknown host factors leading to less hair loss.

●Kerion – Kerion is a severe manifestation of tinea capitis resulting from an intense immune response to the infection.

Kerion is characterized by the development of an inflammatory plaque with pustules, thick crusting, and/or drainage (picture 2) along with regional lymphadenopathy (cervical, retroauricular, and/or suboccipital). A suppurative folliculitis may be the initial presentation [24]. Tenderness or pain is often present. Persistent kerion can lead to scarring alopecia [25]. (See 'Etiology' above.)

Kerions appear most commonly in children ages 5 to 10 and are rare in infancy [26]. Kerion is most often caused by a zoophilic dermatophyte; however, anthropophilic fungi can also cause a kerion. (See 'Etiology' above.)

●Favus – Favus is a unique clinical presentation of tinea capitis. In favus, perifollicular erythema progresses to the characteristic development of cup-shaped, yellow crusts called scutula (picture 1G) [27]. The scutula contain fungi, neutrophils, dried serum, and epidermal cells. (See 'Etiology' above.)

Scutula eventually coalesce to form adherent masses above areas of severe alopecia. There may be an associated unpleasant odor.

The intense inflammation can result in permanent scarring. If untreated, favus may persist indefinitely [27].

Associated findings — Patients with tinea capitis may exhibit associated clinical findings.

●Lymphadenopathy – Palpable retroauricular, suboccipital, and cervical lymphadenopathy is a frequent finding in patients with tinea capitis, particularly when clinical signs of inflammation are present (picture 4).

●Dermatophytid reactions – Autoeczematization reactions (id reactions) are secondary dermatitic eruptions that occur in association with a localized inflammatory skin disorder. The term "dermatophytid reaction" refers to autoeczematization reactions that occur in association with dermatophyte infections. The pathogenesis may involve an immune reaction to fungal antigens, such as a delayed-type hypersensitivity response.

Dermatophytid reactions often follow the onset of antifungal therapy but may also precede treatment [28]. Patients develop a widespread, pruritic, eczematous eruption characterized by erythematous, scaly papules (picture 5). Involvement of the head, neck, trunk, or extremities is common.

Dermatophytid reactions are managed with treatment of the underlying fungal infection as well as emollients, oral antihistamines, or topical corticosteroids as needed [28]. Oral corticosteroids are reserved for severe cases. (See "Dermatophyte (tinea) infections", section on 'Id reactions'.)

●Other – Infrequently, erythema nodosum occurs in association with kerion [29-31]. (See "Erythema nodosum".)

HISTOPATHOLOGY — 

Histopathologic features of tinea capitis include:

●Fungal elements (arthroconidia or hyphae) within or surrounding hair shafts (picture 6)

●Perifollicular mononuclear infiltrate in the dermis

●Multinucleated giant cells in the dermis (in cases where the hair follicle is disrupted)

The fungi can be highlighted with periodic acid-Schiff (PAS) or Grocott methenamine silver (also called Gomori methenamine silver) stains.

Biopsies of kerions will exhibit an inflammatory reaction with a neutrophilic, granulomatous, or mixed dermal infiltrate [24]. Fungi may be difficult to identify due to the intensity of the inflammatory reaction [32].

DIAGNOSIS — 

Tinea capitis should be strongly considered in children presenting with scale and hair loss on the scalp, particularly if cervical lymphadenopathy is present.

Because the diagnosis is infrequent in adults, a higher index of suspicion is often necessary to recognize tinea capitis in the adult population. Immunocompromised states or immunosuppression may predispose adults to develop tinea capitis.

General approach — Tinea capitis often can be diagnosed based on the physical examination if there are alopecic patches with scaling or black dots consistent with tinea capitis. (See 'Physical examination' below.)

However, we typically obtain confirmatory testing (eg, potassium hydroxide [KOH] preparation, fungal culture, polymerase chain reaction [PCR] test). We routinely obtain a fungal culture or PCR test to identify the causative organism. Some clinicians do not perform a fungal culture or PCR if a KOH preparation is positive. (See 'Confirmatory tests' below.)

Treatment often begins prior to the receipt of fungal culture or PCR test results. (See "Tinea capitis: Management", section on 'Overview'.)

Physical examination

●General approach – The physical examination should include a careful examination of the hair and scalp to identify signs consistent with tinea capitis or suggestive of another disorder. (See 'Clinical manifestations' above.)

The characteristic "black dots" that can occur in endothrix tinea capitis or the classic scutula of favus are helpful signs that strongly suggest a diagnosis of tinea capitis (picture 1F-G). A localized, inflamed, tender, boggy plaque on the scalp is suspicious for kerion (picture 2). (See "Evaluation and diagnosis of hair loss", section on 'Physical examination'.)

Examination of the rest of the skin surface is also prudent to identify skin or nail findings suggestive of another condition. For example, psoriasis or seborrheic dermatitis often presents with scalp disease associated with characteristic eruptions in other body areas. (See 'Differential diagnosis' below.)

Cervical lymph nodes should be palpated because cervical lymphadenopathy is a common, though not ubiquitous, finding in tinea capitis (picture 4). (See 'Associated findings' above.)

●Adjunctive techniques – Wood's light examination and dermoscopy findings can support a diagnosis of tinea capitis.

•Wood's light examination – Examination of the affected area with a Wood's light can help identify tinea capitis in patients with some ectothrix infections and favus.

Ectothrix infections secondary to M. canis often exhibit green-yellow fluorescence under Wood's light illumination [33]. Wood's light illumination of favus secondary to T. schoenleinii can reveal faint blue fluorescence [27]. However, the absence of Wood's light fluorescence does not definitively exclude infection with these organisms [34].

•Dermoscopy – Dermoscopy of the hair and scalp (also known as trichoscopy) may be a useful adjunctive diagnostic measure. (See "Overview of dermoscopy of the hair and scalp".)

Common dermoscopic findings in tinea capitis include broken hairs, dystrophic hairs, corkscrew hairs, comma hairs, and black dots (picture 7) [35-38].

The findings of a study of five children with tinea capitis suggest high-magnification (x150) dermoscopy may identify additional features in tinea capitis, such as horizontal, white bands in hair shafts (barcode-like hairs) and translucent, easily deformable hairs [39]. (See "Overview of dermoscopy".)

A review of 24 children with tinea capitis suggests that dermoscopic findings may vary based on the type of infection [40]. In addition to broken hairs and black dots, children with endothrix infections (eg, T. tonsurans, T. soudanense) exhibited comma hairs and corkscrew hairs, whereas children with ectothrix infections (eg, M. canis, M. audouinii) exhibited barcode-like hairs and zigzag hairs.

Confirmatory tests — Confirmatory tests for tinea capitis include KOH preparations, fungal cultures, and PCR tests.

Potassium hydroxide preparation — A KOH preparation is a rapid method for confirming the presence of a dermatophyte infection. Unlike a fungal culture or PCR test, a KOH preparation does not confirm the causative species.

●Procedure – The clinician plucks several hairs within the involved areas. The clinician then performs a microscopic examination of the proximal ends of the hairs after applying 10% to 20% KOH to the slide. (See "Office-based dermatologic diagnostic procedures", section on 'Potassium hydroxide preparation'.)

●Interpretation – Arthroconidia (fungal spores) are found within the hair shaft in endothrix infections and predominantly outside of the hair shaft in ectothrix infections. KOH preparations of favus demonstrate hyphae and air spaces within hair shafts. (See 'Pathogenesis' above.)

In some cases, clinicians cannot identify fungal elements in KOH preparations from patients with tinea capitis. Accurate interpretation of this test is highly dependent on both the collection of an adequate sample and the clinician's skill in recognizing fungal elements [41]. Special stains can facilitate the visualization of fungal elements. (See "Office-based dermatologic diagnostic procedures", section on 'Potassium hydroxide preparation'.)

KOH preparations may be a less sensitive method for detecting tinea capitis. In one study of 15 patients with suspected tinea capitis who were assessed with three tests (a KOH preparation, fungal culture, and a PCR test) prior to treatment, only nine patients (60 percent) had a positive KOH preparation [42]. All patients had a positive PCR test, and 13 patients (87 percent) had a positive fungal culture.

Fungal culture — Fungal cultures can confirm tinea capitis and identify the causative species. However, culture results may not be available for several weeks and generally should not delay the initiation of treatment. (See "Tinea capitis: Management", section on 'Overview'.)

●Procedure – To obtain a sample for culture, the clinician rubs a sterile toothbrush over the affected area or swabs the site with a moistened cotton swab [43-46].

Sending some hairs with the scraping may increase the yield. Infected hairs often break and, thus, come out easily.

Culture can also be performed from a tissue biopsy; however, this is rarely necessary.

●Interpretation – Although fungal culture is considered the gold standard test for tinea capitis, false-negative results can occur [42]. False-negative results are common when fungal cultures are taken from kerion, likely secondary to the intense inflammatory response [47]. In some patients, cultures taken during antifungal treatment of tinea capitis may also be negative, making it difficult to confirm the accuracy of the diagnosis. Other factors that may contribute to false-negative results include improper culture technique and the presence of contaminants that inhibit the growth of the pathogen [41].

Occasionally, nondermatophyte fungi and yeasts, such as Alternaria, Aspergillus, Fusarium, Scopulariopsis, or Candida species, are cultured from patients with clinical findings suggestive of tinea capitis [48-50]. In immunocompetent patients, it can be difficult to determine if these common environmental contaminants are truly acting as pathogens. In immunocompromised patients, nondermatophyte fungi can be important pathogens.

If a nondermatophyte is identified and the diagnosis is unclear (eg, if other causes of scalp scaling, such as sebopsoriasis or eczematous dermatitis, are suspected), then performing a repeat culture to prove the presence of a nondermatophyte fungal infection of the scalp can be helpful. Absence of the same organism on repeat culture suggests a contaminant.

Polymerase chain reaction — PCR techniques, molecular tests that can be utilized to detect fungal deoxyribonucleic acid (DNA), have emerged as an additional option for confirming the presence of dermatophyte infections [42,51]. An advantage of PCR is the potential for more rapid detection and speciation of causative fungi compared with fungal culture.

Factors such as cost and availability are limiting factors for PCR testing [45]. In addition, given that PCR can detect nonviable fungi, PCR can be positive shortly after successful treatment in some patients [42]. (See "Onychomycosis: Epidemiology, clinical features, and diagnosis", section on 'Polymerase chain reaction'.)

DIFFERENTIAL DIAGNOSIS — 

The differential diagnosis of tinea capitis primarily consists of other scalp disorders that may present with scale, pustules, or hair loss. The differential diagnosis varies according to the clinical presentation.

A careful physical examination often reveals features that distinguish other diseases from tinea capitis. Identification of dermatophytes on a potassium hydroxide (KOH) preparation or culture also distinguishes tinea capitis from other diseases.

Examples of disorders in the differential diagnosis based on the clinical findings include:

●Scaly patches with alopecia

•Psoriasis – Well-demarcated, erythematous plaques with coarse scale are characteristic findings of psoriasis (picture 8). Often patients have skin involvement in other areas, such as the elbows, knees, or intertriginous areas. Nail abnormalities, such as pitting, discoloration, onycholysis, and subungual hyperkeratosis, may be present. (See "Psoriasis: Epidemiology, clinical manifestations, and diagnosis", section on 'Clinical manifestations'.)

●Patches of alopecia with black dots

•Alopecia areata – Alopecia areata is an autoimmune form of hair loss that may occur in children and adults. Alopecia areata classically presents with discrete, often circular patches of alopecia (picture 9 and picture 10). Scale is absent. Exclamation point hairs (short hairs up to a few millimeters in length with tapered proximal ends) are a common feature of alopecia areata that may be confused with broken hairs of tinea capitis (picture 11). (See "Alopecia areata: Clinical manifestations and diagnosis", section on 'Clinical features'.)

●Widespread scaling with subtle hair loss

•Seborrheic dermatitis – Seborrheic dermatitis of the scalp presents with diffuse scaling often associated with erythema and pruritus (picture 12A-B). Alopecia is typically absent. Patients may have involvement in other areas, such as the eyebrows, nasolabial folds, and intertriginous areas. Seborrheic dermatitis usually occurs in infants, adolescents, and adults. Prepubertal children usually do not develop seborrheic dermatitis. (See "Seborrheic dermatitis in adolescents and adults" and "Cradle cap and seborrheic dermatitis in infants".)

●Kerion

•Bacterial folliculitis – The suppurative folliculitis that may be an early manifestation of kerion should be distinguished from bacterial folliculitis (picture 13). A Gram stain or culture will reveal the causative bacteria. (See "Infectious folliculitis", section on 'Bacterial folliculitis'.)

•Folliculitis decalvans – Folliculitis decalvans is an uncommon form of cicatricial (scarring) alopecia that presents with one or more patches of alopecia with associated pustules. Follicular orifices typically are absent within the areas of alopecia, consistent with scarring. Tufted hairs (multiple hairs emerging from a single follicular orifice) are a common finding (picture 14). Unlike tinea capitis, folliculitis decalvans almost exclusively occurs in adults. Scalp biopsy confirms the diagnosis. (See "Folliculitis decalvans".)

•Dissecting cellulitis – Dissecting cellulitis is an uncommon form of cicatricial alopecia characterized by the development of follicular papules, pustules, fluctuant nodules, and abscesses on the scalp (picture 15). Biopsy confirms the diagnosis. (See "Dissecting cellulitis of the scalp".)

●Scutula

•Various disorders – Recognition of the characteristic cup-shaped scutula strongly suggests a diagnosis of favus. In less classic cases, disorders such as psoriasis (picture 8), discoid lupus (picture 16), pityriasis amiantacea (picture 17), and the cradle cap presentation of seborrheic dermatitis (picture 18) may enter the differential diagnosis.

Examples of other disorders that may enter the differential diagnosis of tinea capitis are trichotillomania (trichotillosis) and pediculosis capitis.

●Trichotillomania – Trichotillomania is a condition in which the patient manipulates or pulls the hair, often resulting in unusual configurations of hair loss (picture 19). Scale and inflammation are absent. (See "Skin picking (excoriation) disorder and related disorders", section on 'Trichotillomania'.)

●Pediculosis capitis – The pruritus associated with pediculosis capitis may lead to suspicion for tinea capitis. However, the visualization of lice or nits on physical examination confirms pediculosis capitis (picture 20). In contrast to tinea capitis, scale is minimal or absent. (See "Pediculosis capitis", section on 'Clinical manifestations'.)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Dermatophyte infections".)

SUMMARY AND RECOMMENDATIONS

●Overview – Tinea capitis is a common fungal infection of the scalp and hair that most commonly occurs in children. Dermatophytes in the genera Trichophyton and Microsporum are responsible for almost all cases of tinea capitis. (See 'Epidemiology' above and 'Etiology' above.)

●Forms of infection – Dermatophyte infection of the hair may present in three forms: endothrix infection, ectothrix infection, or favus. In endothrix infection, arthroconidia (fungal spores) are present within the hair shaft. Arthroconidia in ectothrix infections primarily surround the hair shaft. Favus is characterized by hyphae and air spaces within the hair shaft. (See 'Pathogenesis' above.)

●Clinical manifestations – Tinea capitis has multiple clinical presentations. The most common manifestations are scaly patches with alopecia and patches of alopecia with black dots at follicular orifices that represent broken hairs (picture 1A-F).

Other manifestations include widespread scaling on the scalp with subtle hair loss (picture 3), kerion (an inflammatory, boggy plaque (picture 2)), and favus (picture 1G). Scutula (cup-shaped, yellow crusts) are a characteristic finding in favus. (See 'Clinical manifestations' above.)

Cervical lymphadenopathy is common. Secondary dermatitic eruptions (dermatophytid reactions) may also occur (picture 5). (See 'Associated findings' above.)

●Diagnosis – The diagnosis of tinea capitis can often be made based on the physical examination. We typically also obtain either a fungal culture or polymerase chain reaction (PCR) test to confirm the diagnosis and identify the causative organism. (See 'Diagnosis' above.)

We often perform a potassium hydroxide (KOH) preparation. When positive, a KOH preparation provides immediate confirmation of the diagnosis but cannot confirm the causative organism. (See 'Diagnosis' above.)

●Differential diagnosis – The differential diagnosis of tinea capitis is broad and based on the clinical findings. Common disorders in the differential diagnosis include psoriasis, alopecia areata, and seborrheic dermatitis. (See 'Differential diagnosis' above.)