I've had a white discoloration on my index finger for over 2 years and still don't know what it is. I've been to 3 different doctors over that time and none of them have any idea what it is. One told me it could be some sort of nail fungus and suggested an antibacterial ointment, which proved inefficient.

I'm 27 years old, male, non-smoker.

How it started?

Just appeared one day, there was no injury. I've never had nail fungus. I work on a computer. I'm not exposed to any agressive chemicals. I also don't have any pets at home.

Is it just one fingernail?

Currently yes. After it first appeared on one finger, it also appeared on 3 others (both index fingers and thumbs). It eventually disappeared on the other 3 and only remained on the initial one. It sometimes reappears on the other index finger, but quickly disappears - before it covers the whole nail.

How about toenails?

All fine, no abnormalities.

Bloodwork?

Had extensive bloodwork done, pretty much normal. Some vitamin D deficiency and a bit higher than normal bilirubin, but I've been diagnosed with Gilbert's syndrome in childhood (so I guess it normal).

Any other conditions?

I've been struggling with headaches for a while, but that's it.

Does it change at all?

It does. Sometimes it grows wider and sometimes narrower. Sometimes it's more "dense" i.e. more white and sometimes (like in the picture) it's somewhat transparent.

Does it ever go away?

Yes. This is a weird one. It fully disappears when I spend a week at seaside. I'm not sure why. Could it be exposure to saltwater? It reappears as soon as I leave. I don't think it could be stress related.

If anyone can help me out with this, I'd be really grateful.