Description, Causes and Risk Factors:
White piedra is a superficial cosmetic fungal infection of the hair shaft caused by Trichosporon beigelii. Infected hairs develop soft grayish-white nodules along the shaft. Essentially no pathological changes are elicited. White piedra is found Worldwide, but is most common in tropical or subtropical regions.
The Mycology of Trichosporon spp. is extremely complicated because the designation refers to a heterogeneous group of organisms. The heterogeneity results from the absence of simple methods to distinguish between the species in the clinical microbiology laboratory; thus, multiple members of the genus Trichosporon were previously categorized together under the name T. beigelii. With the use of modern molecular biological techniques, some mycologists have proposed a re-arrangement of the genus. The proposed names for the six main species associated with human infection are T. asahii, T. asteroides, T. cutaneum, T. inkin, T. mucoides, and T. ovoides.
White piedra can often be confused with pediculosis or lice infestation. Infections can co-exist with dermatophyte or Candida infections, and erythrasma, a bacterial skin infection characterized by reddish brown, slightly raised patches, especially in the armpits and groin. White piedra should be differentiated from tinea capitis (a skin and hair follicle infection), and trichomycosis axillaris (an infection of the axillary and pubic hairs with the development of yellow, black, or red concretions around the hair shafts).
The mode of infection is unclear. There is probably person-to-person transmission, but also geophilic sources appear involved. This disease is more common in temperate climates and has been reported in South American, Canada, Australia, Eastern and Central Europe. Rarely this incidence has been reported in Japan. Although it has been reported from many parts of Asia, it is less common in the tropics.
It is characterized by soft white nodules similar to nits but can be easily pulled off, unlike nits. The nodules may be white, pale green or yellow and are composed of compact fungal elements. The hairs are not invaded but they may break if the fungi have been there for long period. Occasionally, the adjoining skin can get infected, especially in areas like the groin, causing intertrigo, which is considered as a form of cutaneous trichosporosis.
Diagnosis may include following tests:
Direct Microscopy: Hairs should be examined using 10% KOH and Parker ink or calcofluorwhite mounts. Look for irregular, soft, white or light brown nodules, 1.0-1.5 mm in length, firmly adhering to the hairs.
Culture: Hair fragments should be implanted onto primary isolation media, like Sabouraud's dextrose agar. Colonies of Trichosporon beigeliiare white or yellowish to deep cream colored, smooth, wrinkled, velvety, dull colonies with a mycelial fringe.
Serology: Rarely required for diagnosis.
Identification: Characteristic clinical, microscopic and culture features.
Clinical Material: Epilated hairs with white soft nodules present on the shaft.
The disorder can be controlled by shaving and by local application of 5% ammoniated mercury ointment, topical 2% miconazole, 2% ketoconazole or 1% terbinafine four times a day for a period of 2 weeks or till remissions occur. Oral itraconazole therapy has also been suggested. Although it relapses frequently, removal of the affected hair is usually curative, with few recurrences.
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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