Splinter hemorrhages are distinctive physical signs appearing underneath the fingernails or toenails. They are named for their appearance, which closely resembles a tiny wooden splinter lodged beneath the nail plate. These marks are small areas of bleeding from the capillaries in the nail bed, the tissue directly beneath the nail itself.
The hemorrhages manifest as thin, dark lines, typically measuring between one and three millimeters in length. They run vertically, aligning with the direction of nail growth, and are fixed to the nail bed, meaning they do not disappear when pressed. Initially, the marks may appear bright red, but they darken to a reddish-brown or black color as the blood clots and ages.
Trauma and Minor Causes
The most frequent cause of a splinter hemorrhage is direct physical trauma to the nail unit. A sudden, sharp impact, such as hitting a finger with a hammer or stubbing a toe, can rupture the small, longitudinally arranged blood vessels in the underlying nail bed. These hemorrhages resolve spontaneously as the nail grows out.
Repetitive microtrauma can also be a cause, particularly in athletes or those who wear ill-fitting footwear. Constant, minor stress on the nails can lead to capillary damage and bleeding. When caused by localized injury, the hemorrhage is usually confined to one or two nails, and the mark typically appears toward the distal, or outer, edge of the nail.
Certain medications increase the likelihood of developing these hemorrhages due to their effects on blood clotting. Anticoagulant medications, such as aspirin or warfarin, inhibit the ability of platelets to stop bleeding. While they do not directly cause capillary damage, they make the nail bed more prone to noticeable bleeding following minor stress.
Other systemic factors not related to serious illness may also contribute. These include certain cancer medications, specifically tyrosine kinase inhibitors, which can affect the growth and repair of the nail bed capillaries. A percentage of cases are classified as idiopathic, meaning the hemorrhages appear in otherwise healthy individuals without any identifiable underlying cause.
Underlying Systemic Conditions
While trauma accounts for most isolated cases, splinter hemorrhages appearing without a clear history of injury can indicate a serious underlying systemic condition. These conditions typically damage small blood vessels or introduce foreign material that obstructs blood flow in the nail bed capillaries. The primary concern is infective endocarditis, an infection of the inner lining of the heart’s chambers and valves.
Infective endocarditis involves the formation of infected clots, or vegetations, on the heart valves. Fragments of these vegetations break off and enter the bloodstream as microemboli. These tiny infected particles travel to smaller vessels, including the capillaries of the nail bed, causing obstruction and localized bleeding. Splinter hemorrhages are observed in patients with this heart infection, requiring immediate medical evaluation when present alongside other symptoms.
Other systemic diseases involving inflammation and damage to blood vessels, known as vasculitis, can also lead to splinter hemorrhages. Conditions like systemic lupus erythematosus or rheumatoid arthritis involve uncontrolled inflammation that compromises the structural integrity of capillaries throughout the body. The resulting damage and leakage of blood into the nail bed tissue create the characteristic linear streak.
Splinter hemorrhages are also associated with various dermatologic and autoimmune disorders. Psoriasis, a skin condition, can involve the nail matrix and bed, making them more fragile and susceptible to bleeding. Additionally, conditions that predispose individuals to abnormal clotting, such as antiphospholipid syndrome, can result in micro-occlusions in the nail bed capillaries.
When to Seek Professional Diagnosis
The distinction between a benign, trauma-related hemorrhage and one signaling a serious systemic condition lies in the pattern and accompanying symptoms. A professional evaluation is warranted if the hemorrhages appear on multiple nails, or bilaterally on both hands or feet, without a corresponding injury. The location is also an important diagnostic clue, as those related to systemic disease are more often found in the proximal portion of the nail bed.
The presence of systemic symptoms alongside the hemorrhages is a strong indicator of an internal issue. These symptoms can include unexplained fever, chronic fatigue, a new or changing heart murmur, or unexplained joint pain. These findings suggest the possibility of an ongoing infection or an active inflammatory process.
A healthcare provider will typically begin with a detailed physical examination, including a thorough check of the heart and circulation. Diagnostic steps often involve blood tests, such as a complete blood count and a blood culture, to check for signs of infection or systemic inflammation. If infective endocarditis is a concern, an echocardiogram (an ultrasound of the heart) may be ordered to visualize the heart valves and detect any abnormal growths.
Identifying the root cause is necessary to manage the condition effectively. Hemorrhages caused by systemic disease will not resolve until the underlying disorder is treated. While trauma-related hemorrhages require no specific treatment and grow out with the nail, early diagnosis and intervention are necessary for serious underlying issues to prevent severe complications.