Welcome to Japanese maple cultivars. I don't plant them anymore. If it were mine I would take it out, if you would rather struggle with the problem first find out what it is - I would try Washington State University Cooperative Extension.

For an overview (notice more than one listing of maple as being among those plants afflicted)...

Here is a link that might be useful: Pruning out Disease to Keep Trees Healthy

I had a vine maple that had it, probably from the time I planted it. One branch after another started rapidly dying off. I was told that if you cut an afflicted branch, you can see black streaking in the wood which was the case in this tree. After some agonizing, watching branch after branch die and fruitless searching for a cure, I finally took the whole tree out. And, after checking for plants that are resistant, I replaced it with a jacquemonti birch which is thriving. Good luck to you!

I'd cull it.

As bboy wrote, I don't plant them much myself either.

We bought a house with a nice big red one about 15' tall with a nice round-headed habit. That's plenty.

Look at Stewartia, Chitalpa and maybe a dogwood.

Ever seen Smoke Tree properly pruned to become a tree and not a bush? If you can find a taller one, that might be an option.

#16 in the album link below is a tree formed Smoke Tree / Cotinus

Here is a link that might be useful: Album > go to about frame #16 for Smoke Tree in

Sorry.........I lost track of my post and failed to thank everyone for their suggestions!

I had an arborist look at the tree shortly after I posted and he agreed that it was most likely wilt. I pruned all the dead branches out of the tree and gave it one more year. Truth is, I was busy with other projects and really didn't want to tackle replacing the tree.
It's now a year later and it's condition has worsened. Lots of suckers, and few leaves are on the tips of some branches and the rest looks dead. I'm taking it out next week!

mdvaden........I have a Smoke Tree in the back yard that I've pruned into a tree. It's one of my favorites and I love the many colors it shows thru the seasons.

Anyone know if Japanese Snowbell is resistant to the wilt?

There are two other causes that are mistaken for Verticillium Wilt. Not enough water during the summer will cause some branches to die back. The other is too much sun on the trunk causing sunburn and damaging the bark. A tree planted at the corner of a house may not be getting enough water to grow in a healthy manner. That, combined with a lot of sun on the trunk, can be disastrous.
The obvious solution is to move the tree to a more favorable location.