Trichomycosis nodularis: causes, symptoms, diagnosis, and treatment

Trichomycosis nodularis, also known as piedra, is a fungal infection in the hair shaft, characterized by irregular nodules.


The disease can be divided into black piedra and white piedra according etiology and clinical features. The former is caused by piedraia hortae, and the latter is caused by trichosporon asahii.

Signs and Symptoms

There is no discomfort, but cosmetically unacceptable.

Black piedra is characterized by hard, brown to dark, different sized, small nodules, initially under the hair cuticle of hair shaft, gradually fracturing the hair shaft, mainly invading the hair, as well as eyebrows and eyelashes.

Figure 1 black piedra in microscopy

Figure 2 black piedra in microscopy

White piedra is manifested by soft, white to light brown nodules, gradually fracturing the hair, mainly involving the hair.

Figure 3 white piedra

Figure 4 white piedra in microscopy


On the basis of typical clinical findings and microscopic examinations, the disease can be diagnosed.


The simplest treatment is to shave all the infected hair, and topical 1:2000 mercuric chloride, compound benzoic acid ointment, 3% sulfur ointment, or 2% formalin solution can also be considered.