You should see a dermatologist. Two neurologists have told me this has nothing to do with my CIDP. A dermatologist told me it’s psoriasis of the nails. I have it on five fingernails. It can be treated with steroid injections under the nails, but that doesn’t always work. A light treatment is sometimes used. Or you can have all your affected nails removed surgically and wait a year for new ones to grow in. I have started using a new Kerasol product that causes the damaged, brittle material to gradually peel off and make room for new growth. I haven’t used it long so I don’t know the ultimate result, but the bad stuff is coming off in strips (no pain) and I see new growth at the bottom of each nail.