I have DUPA, skin/nails psoriasis and ankylosing sponditilis (it's a chronic inflammatory disease destroying the joints, mainly the spine and hips) All of these diseases appeared at the same time, in 2017. I think they are all related.
In 2019 i did a 15 days water fast and the psoriasis and the inflammation in joints completely disappeared. But the symptoms came back a few weeks after breaking the fast. I have a terrible diet, with lot of junk food. I am 100% sure bad gut health is responsible for psoriasis and AS but i dont know about DUPA.
Anyway, fasting is beneficial for a lot of things. I am going to fast 36 hours every week