Ultrastructural aspect of the keratinolytic activity of piedra.

Piedra are asymptomatic superficial mycoses that form nodules on hair shafts, with two types: white piedra caused by Trichosporon spp. and black piedra by Piedraia hortae. White piedra forms soft nodules that are easily removed, while black piedra forms hard nodules. Traditionally, it was believed that these fungi did not destroy hair cortex keratin but disrupted the cuticle. However, recent ultrastructural research revealed that Piedraia hortae are keratinolytic, dissolving both cuticular and cortex keratin. The chapter discussed these findings and the keratinophilic and keratinolytic activities of these fungi.