Beau's lines

Beau's lines
Beau's lines on the middle fingernail of the left hand caused by a severe paronychia infection
SpecialtyDermatology 

Beau's lines are deep grooved lines that run from side to side on the fingernail or the toenail. They may look like indentations or ridges in the nail plate.:657

This condition of the nail was named by a French physician, Joseph Honoré Simon Beau (1806–1865), who first described it in 1846.