Splinter hemorrhages were first described in 1920 by Sir Thomas Horder in association with bacterial endocarditis. They occur in 15%-33% of patients with infective endocarditis (see acute bacterial endocarditis, subacute bacterial endocarditis).

Overall, estimated prevalence for splinter hemorrhages is about 19%, and they are more common in men than women and in patients of African descent than those of Northern European descent. Fingernails are more often involved than toenails. Typically, only one fingernail is involved. In manual workers, splinter hemorrhages are most common on the right thumbnail and the right second fingernail, presumably due to trauma.

Besides occurring secondary to external manual trauma, splinter hemorrhages may be seen in the setting of a wide variety of dermatologic and systemic conditions. In addition to infective endocarditis, other reported associations are nail psoriasis, nail lichen planus, antiphospholipid syndrome, thromboangiitis obliterans, vasculitis, meningococcemia, high altitude, and medications. Splinter hemorrhages present in 60%-70% of patients taking multikinase inhibitors, typically in the first 2 months of treatment. Other associations include onychomatricoma, onychopapilloma, and tuberous sclerosis.

Pathophysiology is not completely understood. It is thought that splinter hemorrhages are caused by disturbance of nail bed spiral arteries and become longitudinal due to the natural grooves and ridges of the nail plate.