Description, Causes and Risk Factors:
ICD-10-DC: B36.8, B36.3/B36.2
A fungus disease of the hair characterized by the formation of numerous waxy, small, firm, nodular masses on the hair shaft.
The environment and typical skin flora are the two main sources of infectious agents that cause Piedra. The source of infection in black piedra, P. hortae, appears to be in the soil; however, infection also has been traced to organisms in stagnant water and crops. The source of infection for white piedra, typically T. asahii, can be present in the soil, air, water, vegetable matter, or sputum or on body surfaces. However, the mode of infection in man is not clear. White piedra has been described in horses, monkeys, and dogs.
Trichosporon species may also be causative agents of onychomycosis. A German study showed that among yeasts, they represented 10% of such infections. In addition, T. asahii fungemia may develop in clinically deteriorated patients with or without an underlying hematological malignancy, as in a neutropenic patient with acute leukemia.
In the United States, the occurrence of Piedra may be higher in blacks than in whites; however, many cases may be underreported because nodules of piedra may be inconspicuous.
Infections are usually localized to the scalp but may also be seen on hairs of the beard, moustache and pubic hair. Black piedra mostly affects young adults and epidemics in families have been reported following the sharing of combs and hairbrushes. Infected hairs generally have a number of hard black nodules on the shaft. Black piedra may be confused with trichorrhexis nodosa and trichonodosis but mycological examination will always confirm the diagnosis.
P. hortae, the cause of black piedra, grows slowly on Sabouraud dextrose agar and is not inhibited by cycloheximide. Microscopic examination reveals septate hyphae, chlamydospores, and irregularly shaped hyphal elements.These cultures are of the asexual phase of the fungus. Organisms in the sexual phase are difficult to grow in culture.
T. asahii, the typical cause of white piedra, rarely grows on Sabouraud dextrose agar because of inhibition by cycloheximide, which is present in dermatophyte test medium and in Mycosel and mycobiotic agars. In addition, Trichosporon species grow best at 28-30°C.
Shaving or cutting the hair is the treatment of choice. Antifungal agents and terbinafine also are used in the treatment of Piedra. Black piedra is treated by using oral terbinafine. White piedra can be treated by using topical antifungals, including imidazoles, ciclopirox olamine (PenlacTM, LoproxSM) 2% selenium sulfide, 6% precipitated sulfur in petroleum, chlorhexidine solution, Castellani paint, zinc pyrithione (ZinconSM), and amphotericin B lotion.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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