Are You Confident of the Diagnosis?
Characteristic findings on physical examination
White piedra can occur in patients of any age, and tends to occur in temperate areas of the world. The pubic, axillary, and facial hair are more often affected than scalp hair. Patients have white to light brown soft papules loosely attached at irregular spaces along the hair shaft. They can cause breakage of the hair. Rarely, the cause of white piedra can also cause onychomycosis, or become an invasive skin infection in the immunosuppressed patient presenting as red papules and nodules. A patient’s history may include poor personal hygiene and hyperhidrosis.
Black piedra occurs in warm, humid climates or in travelers returning from these areas. This infection is characterized by black, hard papules (giving the disease its name; piedra means “stone” in Spanish) up to 1-2mm in diameter that are firmly attached to the hair shaft, also at irregular spaces. Black piedra affects the scalp hair more often than facial or pubic hair. The frontal scalp is the most characteristic area affected, although the parietal and occipital scalp may also be involved. The hair may feel gritty but it is not any more fragile. Poor personal hygiene predisposes to this condition as well as to white piedra.
Expected results of diagnostic studies
Diagnosis of both types of piedra can be made by microscopic examination of the nodules on the hair shaft. The hair should be plucked and prepared with 10% potassium hydroxide solution and a fungal stain such as chlorazole black. The nodules of black piedra consist of tightly packed hyphae and spores, and are generally circumferential around the hair shaft, as opposed to nits. White piedra nodules are made up of loosely packed hyphae, arthroconidia, and blastoconidia, are also around the hair shaft circumferentially, and often associated with peripheral bacteria.
Microscopic examination of hair shaft disorders such as monilethrix and trichorrhexis nodosum will reveal their characteristic morphology without fungal hyphae. Wood’s light examination of the affected areas will demonstrate fluorescence in the presence of Corynebacterium that cause trichomycosis axillaris and pubis, but the presence of these bacteria do not rule out a concomitant piedra infection.
Piedraia hortea, the fungus causing black piedra, can be grown on Sabouraud dextrose agar at 25oC. Is not inhibited by cycloheximide, so it will grow on dermatophyte test media. Trichosporon species, which cause white piedra, grow best at 28-30oC, and although they also grow on Sabouraud dextrose agar, they are inhibited by cycloheximide and will not grow on dermatophyte test media.
There is overlap in the differential diagnosis of white and black piedra, and includes pediculosis pubis and capitis, hair casts, monilethrix, trichorrhexis nodosum, trichomycosis axillaris and trichomycosis pubis (which often occurs at the same time as white piedra of the pubic hair).
Who is at Risk for Developing this Disease?
Patients who live or work in unsanitary conditions or who are not able to wash or bath frequently, as well as those who have hyperhidrosis, are at greatest risk for white or black piedra, depending on the area of the world where they live. Sexual contacts of patients with white piedra of the pubic hair may be at increased risk for developing the disease themselves; however, many reports have noted that intimate contacts often remain free of the disease, indicating that there may be an underlying susceptibility in certain hosts.
What is the Cause of the Disease?
White piedra is caused by fungi of the genus Trichosporon. T inkin and T ovoides are the species most likely to be found on pubic hair and scalp hair, respectively. Patients who have white piedra of the pubic hair are likely to have simultaneous pubic hair infection with coryneform bacteria. This bacterial infection of the pubic hair is a condition known as trichobacteriosis or, confusingly, trichomycosis pubis.
Trichosporon species are present in soil, water, air, vegetation, and human and animal sputum and body surfaces. Applying plant oils to the hair for cosmetic or medicinal reasons can encourage or begin infection with Trichosporon species.
Black piedra is caused by the fungus Piedraia hortea, which is ubiquitous in hot, humid environments.
Systemic Implications and Complications
In rare cases of significant immunosuppression such as that seen in advanced HIV infection, Trichosporon species can become invasive and cause red, purple, or necrotic patches or nodules. T asahii has also been reported to cause visceral infection in such cases.
Both black and white piedra can be treated by shaving the hair.
White piedra can also be treated with a variety of topical antifungal agents, including topical imidazoles, ciclopirox, 2% selenium sulfide lotion, Castellani’s paint, pyrithione zinc, chlorhexidine solution, ketoconazole shampoo, econazole or miconazole cream, and topical amphotericin B. Topical keratolytics such as 30% salicylic acid solution can also be used.
White piedra of the scalp in a patient who does not want to shave and who has not responded to topical agents can be treated with oral itraconazole 100mg daily for 8 weeks. White piedra of the genital area that is recurrent can be treated with a combination of shaving and topical antifungals, and ensuring disinfection of undergarments, bedding, and towels. Spontaneous remission of white piedra of the pubic hair has been reported.
Black piedra has been reported to respond to oral terbinafine 250mg daily for 6 weeks, as well as to a variety of topical antifungal and keratolytic agents, but shaving the hair remains the best approach.
Optimal Therapeutic Approach for this Disease
When it is possible to shave the affected area, this is the preferred treatment for both white and black piedra. Genital infections with white piedra often recur, so combining shaving with a short course (1-2 weeks) of a topical antifungal may be warranted for initial treatment. Ensuring that all clothing, bedding, and towels that come in contact with the areas have been washed will help to prevent recurrence.
There have not been randomized controlled trials to determine the most effective topical or oral therapy for white or black piedra, but most topical therapies have been reported to be effective. In widespread cases, cases where the patient is not willing to shave the areas, or cases where applying regular topical therapy may be difficult, oral therapy with itraconazole or terbinafine may be considered, but generally topical therapy and shaving are effective and should be attempted prior to exposing the patient to the risks of systemic therapy.
Patients suspected of having white piedra should be counseled to shave the affected areas, and to apply topical antifungal and antibacterial agents to treat a coinfection with Corynebacterium species. White piedra of the pubic hair can frequently recur, and measures such as disinfecting all garments, bedding, and towels may help to prevent recurrence. Close contacts are not always infected, but should be treated if they are.
Treatment of black piedra should be similar, but often patients do not want to shave their scalp hair. In these cases, antifungal shampoos on a regular basis are useful. Oral therapy with terbinafine can be considered if topical therapy does not cure the condition. Once black piedra has been treated, it is not likely to recur.
Unusual Clinical Scenarios to Consider in Patient Management
Patients immunosuppressed with advanced HIV infection may have widespread infection with white piedra, including the perianal hair. It is important to examine the perianal area in order to discover this infection. All affected areas must be treated to prevent recurrence.
In patients with white piedra of the pubic hair there is often coinfection with Corynebacterium species. This infection can also be treated by shaving the area, or by topical clindamycin in 1% solution or drying agents.
What is the Evidence?
Kiken, DA, Sekaran, A, Antaya, RJ. “White piedra in children”. J Am Acad Dermatol. vol. 55. 2006. pp. 956-61. (A case series of eight children with white piedra in the United States who did not shave their hair, five of whom had clearance with itraconazole 100mg daily and 2% ketoconazole shampoo for one month, and two of whom had clearance with fluconazole 6mg/kg/day and 2% ketoconazole shampoo for 3 weeks.)
Khandpur, S, Reddy, BS. “Itraconazole therapy for white piedra of the scalp hair”. J Am Acad Dermatol. vol. 47. 2002. pp. 415-8. (A case series of 12 patients with white piedra of the scalp who did not shave their hair but were treated with itraconazole 100mg daily until culture negativity was seen. Eleven patients were culture negative at 8 weeks of treatment, and two patients who had been culture negative relapsed within 3 months of finishing treatment.)
Gip, L. “Black piedra: the first case treated with terbinafine (Lamisil)”. Br J Dermatol. vol. 130. 1996. pp. 26-8. (A single case report of a healthy returning traveler from India to Sweden with black piedra of the scalp treated with oral terbinafine 250mg daily for 6 weeks with no recurrence at 2 months following therapy.)
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