Looks an awful lot like rust. That's highly contagious so be careful or it will get your other fuchsias too. It will eventually defoliate the plant and severely weaken it. My personal policy is to toss it and buy a new one. If it's a hard to find variety you might still be able to take a viable/uninfected cutting to restart it before you toss it. I spray the surrounding soil with garden sulphur too.

One year I brought home a fuchsia that infected my entire collection so after that experience I have a zero tolerance policy.

If you're ok with synthetic pesticides there are some fungicides on the market. I've never used them in my garden (and don't plan to start) but I believe immunox might be safe for fuchsias.

Wow that sounds serious. I only have one single fushia plant, so will try to see if it survive after pruning away the intected leaves. My elderly neighbor gave me this so it does have a little sentimental value that a brand new exotic fushia might not have. Thank you for the information, you seem like you have quite a lot of experience with this kind of plant.

Serious in that you need to take some quick action but there are worse problems for a fuchsia. If new growth is still infected I'd suggest you cut it right back and spray with garden sulphur or potassium bicarbonate. If the plant is sentimental I'd suggest you look for an uninfected cutting to start the plant again, just in case.

I mostly grow hardy fuchsias as they love our Pacific Northwest climate. Those that were subject to the rust infection I mentioned did their usual freeze to the ground (harsher than a hard prune) and came back the next spring. I'm sure your's will come back too.