piedra (Monarch Disease Ontology entry MONDO_0000253) is either of two diseases resulting from fungal infection of the hair shafts. Black piedra occurs mainly in and on the hairs of the scalp and is caused by Piedraia hortae; white piedra occurs in and on the hairs of the scalp, beard, mustache and genital areas and is caused by Trichosporon species. Also known as: hair shaft fungal infectious disease.