Remi has been developing rippled areas on his skin. They aren't hard or callused feeling, and don't seem to bother him. After a couple weeks skin will begin to pull away like a scab. He has four areas like this.
The lower area here has already lost a section of skin in the center of the rippled patch. To the right (sorry about the glare) is a patch that looks wet or rough - that's how they start.
This is low on his side - an older patch and a new one beginning below it where some skin is already off, even though it doesn't show rippels yet.
If it matters, Remi is a 15-year-old gelding.
I have Googled this and couldn't find anything about rippled areas of skin. I can not accept that Google has failed me - I must be doing something wrong. If anyone has better luck, or has seen this before, please let me know! If the comments won't work for you here, send an email to firstname.lastname@example.org. Thanks!