Fungal diseases

White piedra

White piedra (or tinea blanca) is a mycosis of the hair^[1] caused by several species of fungi in the genus Trichosporon. It is characterized by soft nodules composed of yeast cells and arthroconidia that encompass hair shafts.

Background

Piedra, which means "stone" in Spanish, is an asymptomatic superficial fungal infection of the hair shaft. In 1865, Beigel^[1] first described piedra in The Human Hair: Its Structure, Growth, Diseases, and Their Treatment; although, he may have been describing Aspergillus infection.

In 1911, Horta classified piedra into 2 types. The first is black piedra, which is caused by Piedraia hortae. The second is white piedra. The etiological agents ofwhite piedra, originally named Pleurococcus beigelii and later Trichosporon beigelii, are now called Trichosporon asahii and 5 other species: Trichosporon ovoides, Trichosporon inkin, Trichosporon mucoides, Trichosporon asteroides,and Trichosporon cutaneum. These 6 organisms are all causative agents of white piedra. T asahii is considered most closely linked to white piedra, although some authorities believe T ovoides is the main agent of white piedra of the scalp. Use of the term T beigelli should be avoided.^[2]

The 2 types of piedra occur in different climatic conditions. Black piedra is most common in the tropical regions of the world that have high temperatures and humidity. For example, black piedra may occur in many central South American countries, including Brazil, as well as in Southeast Asia. Black piedra is rare in the United States. White piedra is more common in temperate and semitropical climates, such as those in South America, Asia, Europe, Japan, and parts of the southern United States.

In addition, the black piedra and white piedra affect the hair in different body locations. Black piedra usually affects scalp hair, whereas white piedra more commonly affects pubic hair, axillary hair, beards, mustaches, and eyebrows and/or eyelashes. However, in Brazil, white piedra is reported to affect scalp hair most commonly.^[3] White piedra affects horses and monkeys, in addition to humans. Black piedra occurs in monkeys and humans.

Both types of piedra ultimately may lead to hair breaking because the shaft is weakened by cuticular penetration. In patients who are immunocompromised, dissemination of T asahii can occur, causing purpuric or necrotic cutaneous papules and nodules. Culture or biopsy samples from skin lesions may reveal the causative organism. Related organisms may be found on animal hair, in soil, or in stagnant water

Black piedra

Description:

Black piedra is a superficial fungal infection of the hair shaft caused by Piedra hortae, an ascomycetous fungus forming hard black nodules on the shafts of the scalp, beard, moustache and pubic hair. It is common in Central and South America and South-East Asia.

Clinical manifestations:

Infections are usually localised to the scalp but may also be seen on hairs of the beard, moustache and pubic hair. Black piedra mostly affects young adults and epidemics in families have been reported following the sharing of combs and hairbrushes. Infected hairs generally have a number of hard black nodules on the shaft. Black piedra may be confused with trichorrhexis nodosa and trichonodosis but mycological examination will always confirm the diagnosis.

Laboratory diagnosis:

1. Clinical Material: Epilated hairs with hard black nodules present on the shaft.

2. Direct Microscopy: Hairs should be examined using 10% KOH and Parker ink or calcofluor white. Look for darkly pigmented nodules that may partially or completely surround the hair shaft. Nodules are made up of a mass of pigmented with a stroma-like centre containing asci.

3. Culture: Hair fragments should be implanted onto primary isolation media, like Sabouraud's dextrose agar. Colonies of Piedra hortae are dark, brown-black and take about 2-3 weeks to appear.

4. Serology: Not required for diagnosis.

5. Identification: Characteristic clinical, microscopic and culture features.

Causative agents:

Piedra hortae

Management:

The usual treatment is to shave or cut the hairs short, but this is often not considered acceptable, particularly by women. In-vitro susceptibility tests have shown that Piedra hortae is sensitive to terbinafine and it has been successfully used, at a dose of 250 mg a day for 6 weeks, to treat a 23 year old Swedish Caucasian man following a 4 month visit to India (Gip, 1994).