Piedraia hortae
| Piedraia hortae | |
|---|---|
| |
| Black piedra nodules on hair | |
| Scientific classification | |
| Kingdom: | Fungi |
| Phylum: | |
| Class: | |
| Order: | |
| Family: | |
| Genus: | |
| Species: | Piedraia hortae
|
| Binomial name | |
| P. hortae (Brumpt) Fonseca & Leão (1928)
| |
| Synonyms[1] | |
Piedraia hortae is a superficial fungus that exists in the soils of tropical and subtropical environments and affects both sexes of all ages.
Morphology
When grown on agar at 25 °C (77 °F) Piedraia hortae grows very slowly
Pathology
| Black piedra | |
|---|---|
| |
| Black piedra nodules on hair |
Piedraia hortae causes the formation of nodules on the hair shaft, a clinical superficial disease commonly known as black piedra.[10] Black piedra is usually seen in tropical regions and it usually targets humans of all ages and targets the scalp, moustache and occasionally pubic hair. The source of the infection is usually in soils, poor hygiene, long hair, cultural use of veils and the application of plant oils to wet hair favours the growth of the infection.[8] Black piedra is a superficial fungal infection, which means that it is restricted to the stratum corneum and causes no inflammation.[11] The infection of the hair shaft results in the formation of nodules on the scalp, moustache and pubic hair. The nodules are hard and gritty,[2] which produce a metallic sound when the hair is combed. The nodules colonize the hair shaft, which causes progressive weakness of the hair and leads to breakage of the hair in severe cases, which can lead to hair loss and baldness. The fungus also has the potential to destroy the cuticular layers of the hair and move into the cortex. Piedraia hortae survives in the scalp is due to the slow rate of the keratin degradation near the cortex and the compact formation of the nodules[6] and the hyphae are tightly packed in black piedra cases.[12] The initial invasion of human hair by P. hortae is achieved by using an eroding hyphae, which force their way beneath or between the cuticular layer.[8] The force applied between or beneath the hair cuticle arises from the growth of the fungus itself. The breakdown of keratin is mainly due to enzymatic processes and corresponds to the abundance of localized mitochondria. The breakdown of keratin begins with the cementing material and progresses to the cortex of the hair shaft.[8] In the cortex two types of degradative patterns are produced which are either parallel or vertical to the axis hair shaft. The parallel pattern arises from hyphal separation of the external cortical layers. The vertical pattern is produced by direct hyphal penetration which creates channels that increase in size as the cortex degrades.[8]
Treatment
The infection cannot easily be removed mechanically,
Terbinafine has been used in the treatment.[16]
Cosmetic uses
Black piedra is sometimes cultivated for cosmetic purposes due to social factors that favour a specific hair colour, which makes them more attractive in their society. Several Indian tribes located from Panama have been known to use several methods in order to darken the hair of albino individuals within their community. One of these methods is the cultivation of black piedra for an extensive period of time in the individuals hair.[17] In Malaysia the nodules of black piedra are very attractive and women are encouraged to sleep with their hair buried in the soil to encourage growth of the black nodules.[18]
Similar taxa
The genus Piedraia contains another species known as Piedraia quintanilhae, which is more common in chimpanzees than humans. It differs from P. hortae in terms of the ascospores do not have any attachments.[19] Another species known as Trichosporon biegelii is commonly known to cause white piedra . White piedra is more common in temperate and semitropical climates,[20] such as South America, Asia, Europe, Japan, and parts of the southern United States. Black piedra usually affects scalp hair, whereas white piedra is more commonly found in pubic hair, axillary hair, beards, moustaches, and eyelashes.[21][22] White piedra affects horses and monkeys, in addition to humans and the nodules are white and brown in colour and can be easily detached from the hair shaft. White piedra is treated by using topical and antifungal agents, but a more effective approach is to use itraconazole therapy.[20] Recent studies have shown that the black, lichen-colonizing fungus, Xanthoriicola physciae, is closely related to P. hortae.[23]
See also
References
- ^ "Piedraia hortae (Brumpt) Fonseca & Leão". MycoBank. International Mycological Association. Retrieved 2014-12-09.
- ^ S2CID 28932880.
- ^ S2CID 10420470.
- ^ PMID 20347655.
- ^ ISSN 0196-4399.
- ^ PMID 9061578.
- ^ a b Figueras, M.J. (2008). "New findings in black piedra infection". Journal of Dermatology. 135: 144–161.
- ^ a b c d e Figueras, María José; Guarro, Josep (2000). "Ultrastructural aspect of keratinolytic activity of piedra" (PDF). Revista Iberoamericana de Micología: 136–141.
- ISBN 978-1-4398-1240-2.)
{{cite book}}: CS1 maint: location missing publisher (link - ^ "eMedicine - Piedra : Article by Robert A Schwartz". 2018-04-17. Retrieved 2008-11-08.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Walsh, Thomas (1996). Medical Microbiology. Texas.
{{cite book}}: CS1 maint: location missing publisher (link) - ^ PMID 8543681.
- PMID 24173183.
- ^ Marshall, James (1960). Diseases of the skin. Edinburgh: E. & S. Livingstone. p. 944.
- S2CID 22280222.
- S2CID 22280222.
- PMID 14096368.
- ^ "Infectious Agents". www.americanhairloss.org. AmericanHairLossAssociation. 2010. Retrieved November 13, 2014.
- ^ DoctorFungus (2007). "Piedraia species". www.doctorfungus.com. DoctorFungusCorporation. Archived from the original on November 13, 2014. Retrieved November 13, 2014.
- ^ PMID 12196752.
- PMID 24778538.
- ^ "Aquatic Pathogens". www.env.gov.bc.ca. Province ofBritishColumbia. 2001. Retrieved November 13, 2014.
- PMID 22679593.
