Piedraia hortae

A fungus causing black piedra

Piedraia hortae is a fungus that is the causative agent of black piedra, a superficial fungal infection of the hair shaft. This condition is characterized by the formation of hard, black nodules on the hair, primarily affecting the scalp hair.

Morphology

Piedraia hortae is a dematiaceous fungus, meaning it has darkly pigmented hyphae and spores. The fungus produces ascomata, which are fruiting bodies that contain asci, the sac-like structures where ascospores are formed. The ascospores are ellipsoidal and darkly pigmented, contributing to the characteristic black nodules seen in black piedra.

Pathogenesis

The infection caused by Piedraia hortae is limited to the keratinized structures of the hair shaft. The fungus adheres to the hair and forms nodules by producing a cement-like substance that binds the fungal elements to the hair. The nodules are hard and gritty, and they can be felt as irregularities along the hair shaft.

Epidemiology

Black piedra is more prevalent in tropical and subtropical regions, particularly in areas with high humidity. It is commonly found in parts of South America, Central America, and Southeast Asia. The infection is more frequently observed in individuals with long hair, as the longer hair provides more surface area for the fungus to colonize.

Clinical Presentation

Patients with black piedra typically present with black, hard nodules on the hair shafts. These nodules are often asymptomatic, but they can cause cosmetic concerns. In some cases, the nodules may lead to hair breakage or damage. The condition is usually diagnosed through clinical examination and confirmed by microscopic examination of the hair.

Diagnosis

Diagnosis of black piedra involves the examination of affected hair under a microscope. The presence of black nodules and the identification of the characteristic ascospores and hyphae confirm the diagnosis. Culture of the fungus can also be performed, but it is not routinely necessary for diagnosis.

Treatment

The primary treatment for black piedra is the removal of infected hair. This can be achieved by shaving or cutting the hair short. Antifungal shampoos containing ketoconazole or selenium sulfide may also be used to help eliminate the fungus. In persistent cases, oral antifungal medications such as terbinafine may be prescribed.

Prevention

Preventive measures include maintaining good hair hygiene and avoiding sharing personal hair care items. In endemic areas, individuals may be advised to keep hair short to reduce the risk of infection.

Related pages

• Fungal infection
• Dermatophyte
• Tinea capitis