Splinter hemorrhage

A splinter hemorrhage is a small blood clot that runs vertically under a fingernail or toenail. They are usually caused by trauma, but can be a symptom of several other conditions that cause clots, such as scleroderma, lupus, arthritis or vasculitis. Even with these conditions, splinter hemorrhages are not always seen, so although they can be part of a differential diagnosis, they are not definitive by themselves. 
Splinter hemorrhage at Wikipedia
Category:Symptoms