| Beau's lines | |
|---|---|
| Classification and external resources | |
| ICD-10 | L60.4 |
| ICD-9 | 703.8 |
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.[1]:657 This condition of the nail was named by a French physician, Joseph Honoré Simon Beau (1806–1865), who first described it in 1846.
Beau's lines are horizontal, going across the nail, and should not be confused with vertical ridges going from the bottom (cuticle) of the nail out to the fingertip. These vertical lines are usually a natural consequence of aging and are harmless.[2][3] Beau's lines should also be distinguished from Muehrcke's lines of the fingernails. While Beau's lines are actual ridges and indentations in the nail plate, Muehrcke lines are areas of hypopigmentation without palpable ridges; they affect the underlying nail bed not the nail itself.
There are several reasons that humans get Beau's lines. It is believed that there is 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. Some other reasons for these lines include trauma, coronary occlusion, hypocalcaemia, and skin disease. They may be a sign of systemic disease, or may also be caused by an illness of the body, such as diabetes, psoriasis, certain drugs—including beta blockers according to the Cleveland Clinic, as well as other drugs used in chemotherapy—or even malnutrition.[4]
Human nails grow at a rate which varies with many factors age, sex and the finger or toe in question as well as nutrition. However, typically in healthy populations fingernails grow at about 0.1mm/day and toenails at about 0.05mm/day.[5] With this in mind the date of the stress causing Beau's lines and other identifiable marks on nails can be estimated.
A researcher found Beau's lines in the fingernails of two of six divers following a deep saturation dive to a pressure equal to 305 meters of sea water, and in six of six divers following a similar dive to 335 meters.[6]
Beau's lines can also be seen one to two months after the onset of fever in children with Kawasaki disease.[7]
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