Ultrastructure of black piedra.

Black piedra or nodular trichomycosis is a superficial mycosis of the hair shaft, prevalent in the tropical areas of South America and Asia and caused by the fungus Piedraia hortai. By scanning electron microscopy the invasion of the hair keratin and the elimination of spores through canals was seen. Transmission electron microscopy showed a complex, well-organized microsystem, in which cement-producing hyphae constitute the pseudoparenchyma. Both sexual and asexual reproduction were found. Sexual reproduction gives rise to ascospores and asexual reproduction to arthrospores. The ascospores were found in thick-walled bags, the asci; the arthrospores, that undergo gemmation, are eliminated through canals, disseminating the disease.