| piedra | Either of two diseases resulting from fungal infection of the hair shafts. Black piedra occurs mainly in and on the hairs of the scalp and is caused by piedraia hortae; white piedra occurs in and on the hairs of the scalp, beard, moustache and genital areas and is caused by trichosporon beigelii. (12 Dec 1998) |
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| piedra nostras | A condition similar to piedra, but affecting the hair of the beard. (05 Mar 2000) |
| Piedraia | A genus of fungi, based on Piedraia hortae, which is probably the only species and which causes black piedra. Origin: see piedra (05 Mar 2000) |
| black piedra | Piedra involving the hairs of the scalp, caused by Piedraia hortae and characterised by firmly adherent black, hard, gritty nodules composed of an organised, firmly cemented mass of fungus cells; the fungal growth is always located above the level of the hair follicles; the disease occurs in humid tropical countries of the Americas, Africa, Southeast Asia, and Indonesia, and attacks chimpanzees and other primates as well as humans. (05 Mar 2000) |
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| white piedra | <microbiology> A fungal infection (tinea albigena) caused by the yeast Trichosporon beigelii that forms light-coloured nodules on the beard and mustache. (13 Nov 1997) |