Following carotid endarterectomy, a patient received chloramphenicol for a postsurgical complication. Subsequently his fingernails, which had been black, began to return to normal color. Since chloramphenicol-sensitive Proteus mirabilis was cultured from the nails, this organism may have been responsible for the black pigment. P mirabilis should be considered when a patient is seen with dark-brown or black nails.
Zuehlke RL, Taylor WB. Black Nails With Proteus mirabilis. Arch Dermatol. 1970;102(2):154-155. doi:10.1001/archderm.1970.04000080026005