Piedra

INTRODUCTION — Piedra, the Spanish word for "stone," is a descriptive name for fungal infections that cause small, stone-like concretions on hair. Piedra is divided into two subtypes: white piedra and black piedra.

White piedra presents with white to brown nodules on hair shafts on the scalp, axillae, groin, or other hair-bearing areas and is caused by multiple species of fungi of the genus Trichosporon, of the class Basidiomycetes (picture 1). Black piedra is caused by the fungus Piedraia hortae, of the class Ascomycetes, and presents with darker-colored nodules on hair shafts. Black piedra typically occurs on the scalp.

The clinical manifestations, diagnosis, and management of piedra, with a focus on white piedra, will be reviewed here. Other hair shaft abnormalities and additional manifestations of Trichosporon infections are reviewed separately. (See "Hair shaft disorders" and "Evaluation and diagnosis of hair loss", section on 'Inherited and acquired structural hair disorders' and "Infections due to Trichosporon species and Blastoschizomyces capitatus (Saprochaete capitata)".)

WHITE PIEDRA

Epidemiology and risk factors — White piedra is an uncommon fungal infection that most frequently occurs in humid, tropical climates but also occurs worldwide [1]. The infection has a predilection for children and young adults, particularly females [2,3]. In a systematic review of published reports of white piedra on the American continent, 89 of 106 patients (84 percent) were under the age of 15 years and over 90 percent of patients were female, with most cases occurring in Mexico or South America [3].

Predisposing factors to infection may include persistent, warm, moist conditions; long hair, especially when tied up or occluded with hair coverings or oil; and poor hygiene [2,4].

White piedra can also occur in animals, such as horses and monkeys [5].

Mycology — Trichosporon species, the cause of white piedra, are saprophytic yeasts that can colonize the skin and hair [4]. Historically, white piedra was attributed to infection with a single organism, Trichosporon beigelii [6]. However, advances in molecular identification techniques have resulted in reclassification of T. beigelii and the identification of Trichosporon inkin, Trichosporon ovoides, Trichosporon asahii, Trichosporon cutaneum, and Trichosporon mucoides as the major causative organisms of white piedra [1,3,7-9]. (See "Infections due to Trichosporon species and Blastoschizomyces capitatus (Saprochaete capitata)", section on 'Mycology'.).

The likelihood of infection with specific Trichosporon species appears to correlate with the infection site. T. asahii, T. cutaneum, and T. mucoides are common causes of scalp infection, whereas T. inkin is commonly found in genital infections [2]. T. inkin has also been identified in white piedra of the scalp [1,3,10-13].

Candida parapsilosis is another fungal species that has been implicated in white piedra, both synergistically with Trichosporon and as the sole pathogen [11,14].

Pathogenesis — The mode of transmission of white piedra is unclear. Trichosporon species have been isolated from the environment and other body sites, and observations of concomitant disease in family members suggests that close contact with infected individuals can play a role [2,8,15,16].

An in vitro model of white piedra suggests that the fungus contacts and adheres to the hair shaft, then encircles the hair, and ultimately forms a mature, compact nodule through excretion of a cement-like substance [17]. The fungus surrounds the hair shaft in a sheath-like fashion and sometimes invades the cortex of the hair follicle (picture 2A-B) [6,10]. Coinfection with coryneform bacteria can occur and may enhance the ability of the fungus to penetrate the hair shaft [6,16].

Clinical manifestations — White piedra classically presents with numerous small nodules attached to hair shafts and can affect any hair-bearing area, including the scalp, axillae, genital area, beard, eyebrows, eyelashes, and moustache (picture 1) [18]. Nonscalp involvement may be more common in temperate regions than tropical regions.

The nodules are initially only palpable but enlarge over time, becoming well-defined, soft to somewhat firm, 1 to 3 mm, white to brown nodules [19]. A single hair shaft may have multiple nodules. Severely affected hair shafts can become fragile, resulting in hair breakage. The nodules tend to persist without treatment.

White piedra is asymptomatic, and abnormalities of the underlying skin are usually absent. However, a tinea capitis-like presentation manifesting with scalp hyperkeratosis and alopecia has been reported in children [2].

Diagnosis — A clinical diagnosis of white piedra can be made based upon the presence of white to brown, loosely adherent, circumferential concretions on hair shafts and light microscopy demonstrating fungal elements surrounding hair shafts (picture 2A-B). The diagnosis is confirmed through the detection of Trichosporon species with a fungal culture.

History and physical examination — Patients with white piedra may present with a complaint of persistent, small, palpable bumps on the hair. Examination of the hair shafts with the naked eye demonstrates multiple small nodules attached to hair shafts (picture 1). Early nodules may slide along the hair shaft when manipulated. Older nodules are less likely to be mobile.

Dermoscopy and Wood's light examination are supplemental examination tools that may aid with diagnosis. Dermoscopic examination can facilitate visualization of the circumferential nature of the nodules, assisting with differentiation from nits in pediculosis. A Wood's light examination is typically negative, distinguishing white piedra from trichomycosis (trichobacteriosis), where there is typically yellow-white or yellow-green fluorescence [12]. (See 'Differential diagnosis' below.)

Light microscopy — Direct microscopic examination of a nodule with a potassium hydroxide preparation will reveal fungal elements (spores and hyphae) surrounding the hair shaft (picture 2A-B) [1]. (See "Office-based dermatologic diagnostic procedures", section on 'Potassium hydroxide preparation'.)

Fungal culture — A fungal culture demonstrating Trichosporon species confirms the presence of white piedra. A culture is performed through inoculating affected hairs on Sabouraud's agar with chloramphenicol [6,8]. The microbiology laboratory should be notified when a Trichosporon infection is suspected, to ensure appropriate handling of the specimen.

Differential diagnosis — The differential diagnosis of white piedra includes other abnormalities of hair shafts. In particular, white piedra should be distinguished from black piedra, pediculosis, trichomycosis, and acquired hair shaft disorders:

●Black piedra – Black piedra is a fungal infection that manifests with nodular concretions on hair shafts (picture 3). Nodules are darker and more firmly adhered to the hair shaft than in white piedra, and culture of hair shafts reveals P. hortae. (See 'Black piedra' below.)

●Pediculosis – Louse eggs (nits) in pediculosis capitis or pediculosis pubis form adherent structures to the hair shaft (picture 4). Unlike white piedra, nits do not form circumferential nodules on the hair shaft. Light microscopy or dermoscopic examination is helpful for confirming the presence of nits (picture 5A-B). (See "Pediculosis capitis" and "Pediculosis pubis and pediculosis ciliaris".)

●Trichomycosis – Trichomycosis (also known as trichobacteriosis) is a corynebacterial infection of hair shafts that manifests with soft, malodorous nodules or concretions (picture 6A-B). Concretions of trichomycosis exhibit a creamy appearance and tend to be less well defined than concretions in white piedra. A Wood's lamp examination may reveal yellow-white or yellow-green fluorescence. A potassium hydroxide preparation will show an opaque sheath surrounding hair shafts rather than fungal forms. Of note, coryneform bacteria have been detected on hair shafts in patients white piedra [6,16]. (See "Trichomycosis (trichobacteriosis)" and 'Pathogenesis' above.)

●Hair shaft disorders – Hair shaft disorders, such as trichorrhexis nodosa, monilethrix, and pili torti, can cause irregularities along the hair shaft. Light microscopic examination is useful for detecting features characteristic of these hair shaft disorders (picture 7A-C). (See "Hair shaft disorders".)

Treatment — Although white piedra is a benign, asymptomatic condition, treatment is advised to improve cosmesis, reduce hair breakage, and reduce risk for transmission to cohabitants [4]. In addition, persistent white piedra may be a risk factor for the development of invasive Trichosporon infections in immunocompromised patients. (See "Infections due to Trichosporon species and Blastoschizomyces capitatus (Saprochaete capitata)", section on 'Epidemiology'.)

Overview — White piedra is typically treated through shaving or clipping of affected hair and/or antifungal therapies. Although clinical experience supports shaving or clipping of hair in the affected area as a rapidly effective treatment, social and cosmetic concerns prompt many patients to prefer an alternative approach to treatment. Topical and/or oral antifungal therapies are typically prescribed for these patients; however, data to support these interventions are primarily limited to case reports and case series.

Although efficacy of topical therapy alone or oral therapy alone has been reported, white piedra is often treated with both topical and oral antifungal therapy, with ketoconazole 2% shampoo plus oral itraconazole as a common regimen. The addition of oral antifungal therapy is postulated to promote eradication of the infection through treatment of intrafollicular reservoirs on the scalp [2]. Some authors have proposed that oral antifungal therapy may be more likely to be necessary in patients with long, thick hair, which promotes trapping of moisture [1].

Examples of studies assessing combination topical and oral antifungal therapy include:

●A prospective study suggests accelerated resolution may be a benefit of combination therapy. In the study, 60 female patients with white piedra received topical clotrimazole (1% solution applied twice daily), a combination of topical clotrimazole and oral itraconazole (100 mg twice daily for adults and 5 mg/kg per day for children), or a combination of topical clotrimazole and oral terbinafine (250 mg once daily for adults and 125 mg once daily for children) until clinical and mycologic clearance [20]. Patients treated with clotrimazole and itraconazole had a shorter median time to complete clearance (4 weeks) compared with clotrimazole and terbinafine (8 weeks) and clotrimazole alone (12 weeks). All patients in the study achieved complete clearance.

●In a series of eight children with white piedra of the scalp, treatment with ketoconazole 2% shampoo for two months plus either fluconazole (6 mg/kg per day for three weeks) or itraconazole (100 mg per day for one month) led to resolution of infection.

Other studies document benefit of topical or oral monotherapy:

●In a series of 9 children and 5 adults with white piedra, 11 patients treated with ketoconazole shampoo alone for one to two months achieved resolution [1].

●In a study of 12 consecutive adolescent and young adult females treated with oral itraconazole (100 mg per day until culture negative), 11 achieved culture negativity and cessation of new nodule formation after eight weeks of treatment, although two patients had recurrence of disease during a three-month, follow-up period [4].

Examples of other suggested topical regimens include ketoconazole shampoo plus topical 1 to 5% salicylic acid and use of other topical imidazoles [1,16,21,22]. In another series, 10 patients treated for genital white piedra with econazole nitrate 1% cream twice daily for one to four months had marked clinical improvement, but positive fungal cultures occurred for all patients two weeks after the completion of therapy [21]. A variety of other topical agents with antifungal properties, such as ciclopirox, selenium sulfide, sulfur in petroleum, chlorhexidine, Castellani paint, zinc pyrithione, glutaraldehyde, and amphotericin B lotion, have also been utilized; however, there is minimal literature support for efficacy [18].

Our approach — We suggest shaving or clipping of all hair in the affected area for patients who are willing to do so. For other patients we suggest:

●Ketoconazole 2% shampoo three times per week (eg, Monday, Wednesday, Friday) for two months

and

Oral itraconazole for one to two months (100 mg once or twice daily for adults, 5 mg/kg per day [up to maximum of 100 mg per day] for children)

and

Avoidance of prolonged moisture of the hair (eg, avoidance of tying hair up when wet, drying hair after washing)

Clearance of nodules is the preferred endpoint for treatment. Treatment may be extended if patients have improved at the end of this regimen but clearance of nodules has not been achieved.

White piedra is usually responsive to antifungal treatment. Therefore, when patients fail to improve, reassessment of both the diagnosis and patient adherence to the treatment plan is indicated. If patients with confirmed white piedra fail to achieve resolution of the infection with topical and oral antifungal therapy, shaving or clipping of affected hair may be beneficial.

Recurrence — Recurrence of infection is not uncommon. Recurrences may be managed with a repeat course of treatment. Extension of the original treatment course may be needed.

Additional measures may be helpful for optimizing treatment and reducing risk for recurrence. Examples include minimizing exposure of hair shafts to predisposing factors for piedra, such as prolonged moisture related to tying or covering wet hair and, for patients with pubic hair involvement, discarding or disinfecting underwear [18].

BLACK PIEDRA — Black piedra is a rare infection with the dematiaceous fungus P. hortae. Most infections occur in young men, young women, and children in moist, tropical regions of South America and Asia [23].

Black piedra typically affects scalp hair, with occasional beard, axillary hair, or pubic hair involvement [19]. The clinical features consist of concretions up to a few millimeters in length that are darker and harder than in white piedra and more firmly attached to the hair shaft (picture 3). Ultrastructural studies have shown that the fungus invades the hard keratin of the hair shaft [23,24]. However, hair breakage is uncommon [18].

Findings that should raise suspicion for black piedra are asymptomatic, firm, brown, stone-like concretions on hair shafts. A potassium hydroxide preparation will demonstrate nodules containing spores and hyphae on affected hairs (picture 2C). The diagnosis is confirmed through a fungal culture demonstrating P. hortae. The differential diagnosis includes white piedra, pediculosis, and hair shaft disorders. (See 'Differential diagnosis' above.)

Black piedra can persist for years without treatment [25]. Data on treatment are limited to reports of clinical experience and are insufficient to confirm the best approach. Clipping or shaving of affected hairs has been suggested as the primary mode of treatment [18,19,25]. Some authors have suggested the addition of topical antifungal therapies or topical keratolytics [19]. Successful treatment of a patient with black piedra with terbinafine (250 mg per day for six weeks) without shaving of hair has also been documented [26]. Recurrence after treatment is not uncommon [25].

SUMMARY AND RECOMMENDATIONS

●Overview – Piedra consists of two distinct fungal infections that present with nodular concretions on hair shafts: white piedra and black piedra. White piedra is a manifestation of Trichosporon infections. Piedraia hortae is the cause of black piedra. White piedra and black piedra occur most frequently in children and young adults in tropical climates. (See 'Epidemiology and risk factors' above and 'Mycology' above and 'Pathogenesis' above.)

●Clinical manifestations – White piedra presents with soft to somewhat firm, loosely attached, white to brown nodules on hair shafts and may affect hair on the scalp, axillae, genital area, beard, eyebrows, eyelashes, mustache, or other areas (picture 1). Black piedra usually affects scalp hair and presents with firmly adhered, stone-like, brown concretions on hair shafts (picture 3). (See 'Clinical manifestations' above.)

●Diagnosis – A clinical diagnosis of white piedra or black piedra may be made based upon physical examination and a potassium hydroxide preparation demonstrating characteristic fungal elements (picture 2A-C). A fungal culture demonstrating the causative organism confirms the diagnosis. (See 'Diagnosis' above.)

●Treatment – For patients with white piedra or black piedra, we suggest shaving or clipping of hair in the affected region as first-line treatment (Grade 2C). For patients with white piedra who prefer to avoid hair removal, we suggest combination therapy with ketoconazole shampoo and oral itraconazole (Grade 2C). Avoidance of prolonged periods of moisture in the hair may also be beneficial. (See 'Treatment' above and 'Black piedra' above.)