User:Mr. Ibrahem/Beau lines

Beau lines are groves of varying depths that run across the nail plate. Generally all nails are involved at the same level; though trauma may result in a single nail being affected.

Causes include severe illness, chemotherapy, Raynaud disease, trauma, malnutrition, and pemphigus. In some cases the cause remains unknown. It may be seen with eczema or psoriasis. The underlying mechanism involves disruption in nail growth. As nails grow approximately 1 mm every 8 days, the distance the lines have moved indicate when the causative event occurred. If multiple lines are present within the same nail it indicates multiple causal events.

Treatment is directed at the underlying cause. The lines will grow out and resolve without any specific measures. They are relatively common. They are named after the French physician, Joseph Honoré Simon Beau, who first described them in 1846.