Splinter hemorrhages are horizontal red lines under fingernails. These thin, reddish-brown lines resemble tiny wood splinters. They typically run in the direction of nail growth and can appear on both fingernails and toenails, though they are more frequently observed on fingernails. While often harmless, their presence can sometimes signal underlying health conditions.
Understanding Splinter Hemorrhages
Splinter hemorrhages are small areas of bleeding from capillaries in the nail bed. When these delicate capillaries rupture, blood leaks out and becomes trapped under the nail plate. The blood initially appears reddish or purple, but it can darken to brown or black within a few days as it oxidizes. Their characteristic linear shape is due to the longitudinal orientation of capillaries and grooves within the nail bed. As the nail grows, these discolored lines typically move distally towards the nail tip over weeks to months.
Common Non-Medical Causes
The most frequent reason for splinter hemorrhages is direct trauma to the nail or finger. This can result from everyday activities such as stubbing a toe, hitting a finger with an object, or vigorous cleaning under the nails. Sports injuries, tight footwear, or repetitive hand use can also lead to these minor bleeds. Certain medications, such as blood thinners (aspirin, warfarin), some chemotherapy drugs, and specific kinase inhibitors, can also cause splinter hemorrhages. When caused by trauma or medication, these hemorrhages typically resolve as the nail grows out, usually within a few months.
Underlying Medical Conditions
Splinter hemorrhages can indicate various systemic medical conditions, particularly when they appear without trauma or affect multiple nails. These conditions can impact blood vessel integrity or lead to small clot formation.
Infective Endocarditis
Infective endocarditis, an infection of the heart’s inner lining, is a significant cause. In this condition, tiny blood clots or septic emboli containing bacteria can break off from infected heart valves and travel through the bloodstream. When these microemboli reach capillaries in the nail bed, they can cause damage and bleeding. Splinter hemorrhages are observed in 15–33% of patients with infective endocarditis and may appear later in the disease, often with other systemic symptoms.
Vasculitis
Vasculitis, inflammation of blood vessels, can also lead to splinter hemorrhages. This inflammation can damage capillary walls in the nail bed, resulting in localized bleeding. Autoimmune diseases like Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis can cause vasculitis and are linked to splinter hemorrhages.
Dermatological Conditions
Dermatological conditions affecting the nails, such as psoriasis and lichen planus, can also manifest as splinter hemorrhages. In nail psoriasis, rapid skin cell turnover and inflammation can cause microtrauma and bleeding in the nail bed. Lichen planus, an inflammatory skin condition, can also cause splinter hemorrhages.
Other Medical Conditions
Severe kidney disease, particularly in patients undergoing hemodialysis, can contribute to splinter hemorrhages due to increased capillary fragility and platelet dysfunction. Antiphospholipid Syndrome (APS), an autoimmune disorder characterized by an increased tendency for blood clot formation, can also be associated with splinter hemorrhages, often due to small clots disrupting blood flow. Trichinosis, a parasitic infection from undercooked meat, is a rarer cause. As larvae migrate into muscle tissues, they can cause systemic symptoms including myalgia, fever, and splinter hemorrhages due to microvascular changes.
When to Seek Medical Attention
Consult a healthcare provider if splinter hemorrhages appear without clear trauma. The presence of multiple splinter hemorrhages across several nails, especially closer to the nail base, suggests a systemic underlying condition. Seek medical attention if splinter hemorrhages are accompanied by other symptoms such as fever, unexplained fatigue, joint pain, shortness of breath, or a new heart murmur. Individuals with a history of heart conditions, autoimmune disorders, or a family history of relevant diseases should discuss any new splinter hemorrhages with their doctor. Prompt evaluation can help determine the cause and guide management.