Picture of Leukonychia Striata

Leukonychia striata. Also called Mees' lines, these chalky white horizontal streaks on the fingernail are the result of abnormal keratinization in the nail plate. In many cases, there is no obvious cause, but they could be the result of fever, trauma to the nail or malnutrition. The streaks usually grow out or resolve on their own.
Image Source: © Richard Usatine, MD
Text Source: Journal of the American Medical Association
DermNet NZ
Text Source: Journal of the American Medical Association
DermNet NZ