I’ve taken hydrea most of 22 years, no lines or ridges as you have described.

Yes, I’ve been on Hydroxyurea for under a year. The condition is called Melanonychia, I noticed it months ago and it’s benign and due to the meds. It can be on the toe nails and fingers and mine isn’t that bad except for my right thumb. Look it up!!!

Yeah, i googled it. Seems to be my favorite Thing for my "need to know"