Endocarditis is inflammation in the heart’s inner lining. One possible symptom is splinter hemorrhages, thin red or reddish-brown lines under the fingernails. These lines appear when small blood vessels (capillaries) are damaged.

Endocarditis, an infection in the inner lining of the heart, is a rare condition typically caused by a bacterial infection.

Initially, endocarditis may present as flu-like symptoms. But another possible symptom may include a change to your fingertips, known as splinter hemorrhages. These are thin red or reddish-brown lines that appear underneath the fingernails. In this case, you may need to seek medical attention quickly to treat endocarditis and prevent severe complications.

This article explains how a heart infection can affect other parts of your body and why it’s important to seek medical attention promptly.

Early symptoms of endocarditis typically involve flu-like symptoms, including fever, chills, and nausea. As the condition progresses, it has the potential to affect other parts of your body.

For example, you might notice thin, red or reddish-brown vertical lines that appear under your fingertips and run in the direction that the nail grows.

Known as splinter hemorrhages because they can resemble splinters, these marks are a sign that either blood vessels have become swollen and damaged or small clots have injured the capillaries under the nails.

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While splinter hemorrhages can occur because of trauma to the fingertip and other health issues, it’s important to know that one possible reason is endocarditis. Though other symptoms may be more common, these splinter hemorrhages have traditionally been a part of the clinical criteria for diagnosing endocarditis.

Endocarditis is typically the result of a bacterial infection.

The bacteria responsible for this infection can enter the body through a cut in the skin, surgery, or dental work. They can then travel through the bloodstream to the heart where they can attach to the heart valves or get stuck in the lining and begin to grow.

Small clumps of bacteria can also form at the infection site. They can act like blood clots moving through the bloodstream and negatively affect blood flow to the organs.

In rare cases, endocarditis is a result of a fungal infection. These cases are harder to treat and may be fatal.

People are more likely to develop endocarditis if they have a condition that weakens their immune system, heart valve disease, or a long-term central venous line. Having poor dental hygiene habits, a history of IV drug use, and a previous case of endocarditis may also increase your risk.

Read more about the most common causes of endocarditis and other symptoms of the condition.

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It’s important to notify your doctor if you believe you have a splinter hemorrhage, whether it might be caused by endocarditis, any other condition, or possible trauma. Splinter hemorrhages may indicate a serious health concern requiring medical attention.

Research from 2016 notes that as many as a one-third of people with endocarditis develop splinter hemorrhages.

Splinter hemorrhages were traditionally used to diagnose infective endocarditis, or endocarditis caused by an infection. However, they are not the only symptom of endocarditis.

While a splinter hemorrhage itself is not particularly dangerous, endocarditis is a rare, serious condition that can be life threatening. Outlook can vary based on several factors, including the severity of the infection, the type of pathogen, pre-existing health conditions, and complications.

It’s important to seek prompt medical attention if any symptoms of endocarditis — including splinter hemorrhages — appear. Treatment can prevent the condition from causing severe complications.

There is no specific care required for splinter hemorrhages. But it’s important to talk with your doctor about treating endocarditis, if that’s the cause of your fingernail hemorrhages.

Endocarditis is typically treated with IV antibiotics in a hospital setting. In order to determine the antibiotics necessary to effectively treat an infection, doctors may perform blood cultures and consult with infectious disease specialists.

If you receive an endocarditis diagnosis, you can expect to undergo at least 6–8 weeks of antibiotic treatments, though it’s possible that not all of these treatments will be administered in the hospital.

Treatment may also require surgery to replace heart valves and any implanted materials that are affected, such as pacemakers and defibrillators.

Surgery may also be necessary if endocarditis has affected your heart muscle or other parts of the body. For example, surgery may be required for treating fistulas and draining abscesses.

Endocarditis is a rare but potentially fatal condition that can cause small areas of bleeding under the fingernails. Known as splinter hemorrhages, these may indicate blood vessel damage and that endocarditis is in a later stage.

If you are experiencing splinter hemorrhages or have any symptoms of endocarditis, consult your healthcare team immediately to prevent the condition from progressing and causing severe complications.