Beau's lines are deep grooved lines that run from side to side on the
fingernail
A nail is a protective plate characteristically found at the tip of the digits (fingers and toes) of all primates, corresponding to the claws in other tetrapod animals. Fingernails and toenails are made of a tough rigid protein called alpha-k ...
or the toenail.
They may look like indentations or ridges in the
nail plate.
[Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. .]
This condition of the nail was named by a French physician,
Joseph Honoré Simon Beau (1806–1865), who first described it in 1846.
Signs and symptoms
Beau's lines are horizontal, going across the nailline, and should not be confused with vertical ridges going from the bottom (
cuticle
A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...
) of the nail out to the fingertip. These vertical lines are usually a natural consequence of aging and are harmless.
Beau's lines should also be distinguished from
Muehrcke's lines
Muehrcke's nails or Muehrcke's lines (Leukonychia#Apparent leukonychia, apparent leukonychia striata) are changes in the nail (anatomy), fingernail that may be a sign (medicine), sign of an underlying medical condition. The term refers to a set of ...
of the fingernails. While Beau's lines are actual ridges and indentations in the nail plate, Muehrcke lines are areas of
hypopigmentation
Hypopigmentation is characterized specifically as an area of Human skin, skin becoming lighter than the baseline skin color, but not completely devoid of skin pigment, pigment. This is not to be confused with depigmentation, which is characterize ...
without