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Black lines in fingernails & heart disease

Updated July 19, 2017

Black lines in fingernails often result from splinter haemorrhages--bleeding under the nails. Splinter haemorrhages, which occur because of blood vessel swelling or capillary damage, may signal heart disease or other heart conditions.

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Lines in Fingernails

Lines in fingernails--called splinter or fingernail haemorrhages--can appear in shades of black, red or brown. The term "splinter" refers to the appearance of small vertical lines under the nail bed.

Heart Disease And Splinter Hemorrhages

Splinter haemorrhages generally appear in the later stages of endocarditis, a rare heart valve infection prevalent in those with underlying heart disease that causes inflammation of the heart's inner lining. Another condition, vasculitis, can cause these lines through an extreme allergic reaction that damages skin blood vessels.

Endocarditis And Vasculitis

Endocarditis results from germs that enter through other areas of the body, such as the mouth and infect the heart. This rare condition emerges most often in people with existing heart disease that undergo heart or dental surgeries. People suffering from vasculitis often develop painful skin lesions, such as sores, blisters or hives in different areas of the body.

Other Causes

If a heart condition exists, other serious symptoms appear that cause concern and likely result in health monitoring before splinter haemorrhages materialise. The National Institutes of Health indicate that physical trauma to the nail as well as drug use through injections can also cause splinter haemorrhages.


If recent nail trauma has not occurred, people with dark lines in fingernails should visit a physician for proper diagnosis and treatment of any underlying conditions and causes.

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About the Author

Clementina Altamirano

Clementina Altamirano has written professionally since 1999, been published in "Hispanic Magazine" and has extensive experience with health, food and education communications. She enjoys conveying useful information about a wide variety of topics through clear, concise and helpful articles. Altamirano holds a degree in English from Texas A&M International University.

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