Black and White Piedra

Black piedra (piedraiosis)

Black piedra is a mycosis of the scalp endemic to tropical regions such as South America and Indonesia. The disease is caused by the fungus Piedraia hortae.

Clinical presentation and pathogenesis The fungus colonizes the hair, actively invading its cuticle. Very hard, black nodules measuring about 1 mm in diameter form on the hair.

Pathogen morphology An interesting feature of Piedraia hortae is the difference in its life cycles depending on the habitat environment:

• In vivo (on hair): The fungus undergoes the sexual reproduction stage (teleomorph). Microscopy reveals dark brown, septate, branching hyphae 4–8 µm thick and asci—specific spore-containing sacs.
• In vitro (on Sabouraud agar): Only asexual reproduction (anamorph) occurs in culture. The fungus forms small, dark brown colonies with characteristic velvety margins. They consist of mycelium and chlamydospores.

Topical antifungal drugs are successfully used to treat this mycosis.

White piedra (trichosporonosis)

White piedra is an infection of the hair shafts which, unlike black piedra, can affect not only the scalp hair but also the mustache and beard. Like black piedraiosis, the disease predominantly occurs in countries with tropical climates.

Etiology and clinical presentation The causative agent is the fungus Trichosporon beigelii, which belongs to the Trichosporon cutaneum complex. As the infection develops, the hair cuticle is affected, and hard nodules form around the shaft itself. By coalescing, they form a characteristic greenish-yellow sheath enveloping the hair.

Morphological and cultural properties

• Microscopic examination reveals septate hyphae approximately 4 µm thick.
• When cultured on Sabouraud agar, Trichosporon beigelii forms cream-colored or gray colonies with a wrinkled surface.
• The microstructure of such colonies is represented by septate mycelium, as well as arthroconidia and blastoconidia.

Treatment approaches The management of white piedra is comprehensive:

1. Pharmacotherapy: azole drugs and flucytosine are used.
2. Mechanical and hygienic measures: shaving off the affected hair combined with strict adherence to personal hygiene rules is extremely effective and represents a crucial component of recovery.

Comparative characteristics of pathogens

For ease of memorization, the main differences between the two types of piedra are presented in the table below:

Class and exam questions

What else to study on this topic

• Morphological differences between teleomorph and anamorph using Piedraia hortae as an example
• Microstructure of Trichosporon beigelii: distinguishing arthroconidia and blastoconidia
• Mechanisms of invasion of the hair cuticle by dermatophytes and other fungi
• Specifics of using azole drugs in hair mycoses

Other topics in the section "Epidermophytoses (microsporia, trichophytosis, favus, rubroophytosis, etc.)"

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