I have had a white line that goes vertically down my thumb nail for the past 5 yrs. My nail splits at the end, this can be very painful especially when I snag it on something or it splits open!! Sometimes it will stay connected %26amp; when that happens, a dark vein grows on the underside??? Please help!!! Anyone know what could cause this???Line down thumb nail, splits at end?
Vertical nail ridges like the ones you mention, starting at the cuticle and extending to the tip of the nail are fairly common and don't usually indicate any health problem.
They are usually idiopathic (no known cause) and are often hereditary; sometimes they can be caused by disturbances to the nail-bed caused by injury.
It wouldn't do any harm to show your doctor next time you're there, as changes to the nail-bed can indicate an underlying problem, but as I mentioned, these lines (as long as they're Vertical) are usually harmless.
The darkness you can see when your nail splits is probably just a line of blood or a hematoma caused by the nail and the nail-bed seperating and, because this follows the line of the split, it can sometimes look like a vein.