Beau's lines

Overview
Beau's lines are deep grooved lines that run from side to side on the fingernail. They may look like indentations or ridges in the nail plate. Beau's lines are the result of a temporary cessation of cell division in the nail matrix. This may be caused by an infection or problem in the nail fold, where the nail begins to form, or it may be caused by an injury to that area or a systemic process.

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

Complete Differential Diagnosis of Causes of Beau's Lines (alphabetical):

 * Chemotherapy particularly cytotoxic agents
 * Dermatologic disorders
 * Diabetes
 * Drugs
 * Hypocalcemia
 * Malnutrition
 * Trauma

Physical examination
Nail bed: Beau's lines should be distinguished from Muehrcke's lines of the fingernails. While Beau's lines are actual ridges and indentations in the nail plate, Muehrcke's lines are areas of hypopigmentation without palpable ridges.

Recent Research on Beau's Lines
A researcher found Beau's lines in the fingernails of 6 divers following a deep saturation dive to a pressure equal to 335 meters of sea water, and in 2 of 6 divers following a similar dive to 305 meters.