Pitted toenails
It could be: Psoriasis. If you find tiny holes, grooves, or ridges in your toenails, you may have nail psoriasis. Though most people who experience nail psoriasis also have skin psoriasis (an autoimmune disease that makes skin patchy and irritated), 5 percent of people with nail psoriasis aren’t affected elsewhere.
“If you’ve never been diagnosed with psoriasis, but your toenails have little pits in them, you should get them checked out,” says Pichney. Other symptoms include white patches and horizontal lines across the nails. To treat psoriasis, your doctor may prescribe topical creams or steroids to be injected under the nail.