French physician Joseph Honoré Simon Beau first described "Beau's lines," or transverse ridges...
Nail Clinic: Beau's Lines
Beau’s lines are a result of a variety of conditions, ranging from minor to severe. The most common causes are local injury or exposure to severe cold, both of which decrease the blood flow to the nail matrix.
Any kind of injury to the nail matrix (also called a microtrauma) slows cell division in the matrix, causing transverse ridges to appear. An example is with athletes who do a lot of jogging or long-distance running—they often find Beau’s lines on their toenails from the repeated smashing of the distal edge into the front of the shoe when running or kicking.
But not all injuries are from playing sports; other examples of local traumas include:
Eczema The inflammation in the skin around the nail (the proximal fold) associated with eczema can prevent normal cell division in the nail matrix.
Habit-tic deformity (HTD) A source of repeated, habitual trauma to the nail matrix, HTD occurs when a person habitually picks at or rubs the central cuticle with a neighboring finger, most commonly seen on the thumb.
Subungual hematoma The hematoma can press into the nail matrix affecting nail cell production.
Paronychia Inflammation of the tissue adjacent to the nail, usually accompanied by infection and pus formation.
Onychia Inflammation of the matrix often leading to suppuration—or pus formation—and loss of the nail.
Carpal Tunnel Syndrome A condition caused by compression of the median nerve in the carpal tunnel, which can affect nail growth.
Another cause of Beau’s lines is congenital disease. Acrodermatitis enteropathica (technical jargon for zinc deficiency) causes changes in the skin and sometimes skin infections around the fingernail, which may result in ridges on the nail.
Beau’s lines are also caused by systemic illnesses, which include extreme fevers, measles, mumps, myocardial infarction and exposure to chemotherapy and radiation.
(Yes, this is a long list to remember, but there is good news—you don’t need to memorize all of these causes in order to help your clients.)