Black Piedra

Etiology

Black piedra results from a particular fungal species called Piedraia hortae. This fungal disease is often caused by poor personal hygiene. It is commonly seen in people with long hair and those who use excessive amounts of different hair oils. Practices like prolonged wearing of veils or tight hats may contribute to its development and progression. There are also reports of sexual transmission. The incidence of fungal infections is increasing due to the opportunistic nature of fungal organisms and the prevalence of immunodeficient conditions.[2]

Epidemiology

Black piedra is an infection of tropical and subtropical regions. However, due to global travel, it may also occur sporadically in other regions, including Europe.  The exact mode of spread of piedra is not clear. The use of an infected comb or sharing pillows and bed sheets may be possible factors for transmission.[3] Although piedra can occur at any age, its incidence usually decreases after middle age.[4] The occurrence of both black piedra and white piedra simultaneously in a patient is extremely rare.[5][6]

Pathophysiology

The soil appears to be the primary source of infection in black piedra, although P. hortae, has also been traced in stagnant water and crops. P. hortae can produce sexual spores during the parasitic phase, a unique feature among other pathogenic fungi. Hairs with black piedra isolated from Brazilian Indians were investigated by studying serial sections with light and transmission electron microscopy.[7] P. hortae showed strong keratolytic activity; it was able to destroy both the cuticle and the hair cortex. Two distinct types of cortical digestion emerged. The first was parallel to the axis of hair and was produced by fungal cells that grew separating the external layers of the outer cortex. The second type was produced by active, boring hyphae, which formed channels as they penetrated vertically to the axis of the hair.

In vivo and in vitro studies using electron microscopy and x-ray microanalysis have revealed the presence of elements such as phosphorus, sulfur, and calcium in the nodules that develop on hair and in culture colonies. These elements are part of the extracellular material that compacts the pseudoparenchymatous organization of the fungus. Their presence is due to the capacity of melanin-like pigments to sequester ions. They may form part of the mucopolysaccharides that constitute the extracellular material. Researchers detected contaminants such as aluminum, silicon, and iron on the surface of the nodule, which have links to the residual molecules produced during the breakdown of cuticular keratin.[8] In P. hortae, the extracellular cementing material that holds the nodule together is likely the primary factor responsible for protecting the fungus against environmental attack and desiccation. Moreover, this compact organization can also impair successful treatment, which may explain why an untreated black piedra may run a very chronic course.

Histopathology

In histological sections or 10% potassium hydroxide (KOH) mounts, the nodules are observed to be made up of closely packed brown hyphae held in a mass by a viscous or cement-like substance. At the edges of the nodules, regularly aligned hyphae and arthroconidia, 4 to 8 microns in diameter, can be seen. In the thicker parts, club-shaped asci containing elongated ascospores may be formed. A crushed nodule reveals asci containing 2 to 8 single-celled fusiform ascospores with a single polar filament at each end.

History and Physical

Black piedra is asymptomatic, except for the unsightly nodes visible on hair strands. On examination, the hair shaft shows firmly attached brown-black nodules, which are less than 1mm in size. These nodules are gritty on palpation. The nodules are usually multiple and vary in size from microscopic to 1 mm or more in diameter. They are oval or elongated in shape with their thickness tapering from 1 end to the other or from the middle to the edge. They are composed of a compact cellular substance that surrounds the hair shaft. Hair shafts affected by these nodules become weak and often break at the point of infection. The disease is chronic and can last for months or even years.

Evaluation

Tools for the evaluation of black piedra include:

• Trichoscopy: Hair examination using trichoscopy can provide useful information for accurate diagnosis by differentiating between pseudonits and nits.[9][10][11] It shows multiple oval or elongate-shaped brown-black nodules on the hair shaft.
• Direct microscopic examination: Visualization of the crushed nodules under 10% KOH shows branched hyphae (4 to 8 microns) held together by a cement-like substance. The dematiaceous filamentous hyphae appear as chains of stout thick-walled cells resembling arthrospores. Visualization enhancement can be via lactophenol cotton blue and other colored dyes.
• Fungal Culture: The culture on Sabouraud dextrose agar (SDA) medium at room temperature shows a smooth greenish-black colony with a raised and cerebriform center. The reverse side of the colonies is blackish. While performing the culture, it is noteworthy that cycloheximide does not inhibit this fungus.

The microscopic examination of the colonies shows round, dark brown, globus ascus with ascospores.

Treatment / Management

Shaving the head to remove all the hair is the most effective way to treat this fungal infection. However, this option may not be acceptable to females for aesthetic reasons. Topical antifungal agents, available in the form of creams or shampoos, are effective. Applying 2% ketoconazole or 2% miconazole shampoo once a week for 3 weeks is also effective. Non-surfactant-based leave-on lotions are also an option. Ciclopirox (0.77%) lotion or 1% to 1.5% shampoo have also been used successfully. Older treatments include benzoic acid compound (BPC) ointment or a 1 to 2000 solution of mercury perchloride act as antifungal preparations for application to the hair after shampooing. Oral antifungals such as terbinafine and itraconazole have been used successfully in cases resistant to topical medications.[12][13] A course of 250 mg of oral terbinafine administered once daily for 6 weeks was also found to be effective in treating black piedra.[12] Topical keratolytics, such as 1% salicylic acid, may also be added in cases that are non-responsive to monotherapy with antifungal shampoos.(B3)

Differential Diagnosis

Differential diagnosis for black piedra includes the following:

• Pediculosis capitis: Black piedra is often mistaken for pediculosis capitis, as lice eggs (nits) resemble the black piedra nodules. Nits are oval in shape and white, light gray, tan, or yellowish. They firmly attach to the hair shaft and are difficult to remove. Nits carrying viable eggs are close to the scalp. Diagnostic confirmation is by the presence of viable eggs, nits in various stages (live and viable, open, empty/dead), or adult lice.
• White piedra: Unlike black piedra that most often occurs on the scalp hair and spares other parts of the nonglabrous skin, white piedra caused by Trichosporon spp. manifests as whitish, loose adherent material on the hair shafts that typically but not exclusively involves the scalp hair. Trichoscopy, direct microscopic examination under 10% KOH, and a fungal culture can easily distinguish the 2 conditions. The septate hyphae of Trichosporon, which cause white piedra, are non-dematiaceous.
• Trichorexix nodosa: It is a disorder of the hair shaft characterized by easy breakability of hair and microscopically by nodes on the hair shaft. The microscopic examination of the node reveals a fractured hair. At the point of fracture, there is visible splaying out and release of individual cortical cells from the main body of the shaft of the hair. 
• Monilethrix: It is a rare autosomal dominant hair disease that results in short, fragile, broken hair that appears beaded. Light microscopy, shows the hair shaft has regular elliptical, fusiform, or spindle-shaped swellings that are separated by constricted internodes.

Treatment Planning

Treatment for black piedra includes the following:

• Shaving the head (if culturally appropriate and with patient's willful consent)
• 2% ketoconazole or 2% miconazole shampoo or 1 to 1.5% ciclopirox shampoo applied once-to-twice-a-week for 3 to 4 weeks
• Oral terbinafine 250 mg once daily for 6 weeks
• Oral itraconazole 100 mg twice-a-day after a meal, with a citrus drink for 1 to 2 weeks
• Counseling on maintaining good scalp hygiene and avoiding the sharing of combs, etc

Prognosis

The low spread of infection outside its endemic habitat and the harmlessness of this disease indicate a good prognosis for this fungal infection. With the right treatment, black piedra has a favorable prognosis- patients recover fully with the restoration of normal hair. 

Complications

There are no serious complications of black piedra infection. In the absence of treatment, patients with comorbidities (diabetes, immunodeficiency, and malignant tumors) may develop alopecia. Reports exist of secondary pediculosis (head lice) as well as mixed piedra (black piedra and white piedra occurring in the same individual) in patients with poor scalp hygiene.[14]