I have been reading about finger nails changes. what has been happening to me is just both little finger nails. The nail starts to grow then nail is weak and starts to break and rip. both nails on my lttle fingers on both hands are cut very short almost no nail at all. My other nails are fine. Why just these fingers?? I am still on humira and 15 mg MTX.
I have nail changes, including ridges, pits, lines, and breakage / weak nail. I know that nail changes are a hallmark of PsA.
I tend to have nail changes in the nails closest to an actively inflamed joint, or a finger with active psoriasis. When the joints improve, or the PsA in general calms down, the nail changes improve as well.
My nails used to be pretty bad: on fingers and toes both. Initially, I started Humira just for psoriasis, and my nails improved so much. My old symptoms were nails separating from the beds with lots of what I now know is plaque forming underneath. It was fairly uncomfortable. After a mot h or so on Humira, all of that cleared up and I haven’t had any probs since. It is interesting that those were the first places to show PsA symptoms though. Even today, when I have a flare, the finder joints closest to where the nail P was the worst is where my symptoms will show up first. In the past, I kept my nails pretty short. Otherwise they were subject to pretty inconvenient breakage well below where the nails should attach to the bed, and would then stay tender until they grew out a little. I always kept a coat of clear polish on them just for protection. It didn’t make them look any better, but they didn’t break as often.
Of course, the hope is that when your meds are better managed, this problem will be too. 
thank you Marietta and grumpy cat I know that I have been under a lot of stress with family problem so I know that does not help. I am going to get some clear nail polish. I have been on humira for 3 years and methotrexate for 2 1/2 yrs. I just hope the medicine keeps working. I don't want to have to increase the MTX.
You didn't mention that you were on folic acid. Folic acid and biotin might well be helpful for this. That's not to say that it will cure it, but it may work to minimize this.