Q.Japanese Maple Issue
Maple has come out with patchy leaf growth and leaves that have come out are in poor state. White patches on bark of tree.
Certified GKH Gardening Expert
Those patches on the bark will be unrelated, and are what is known as a Lichen. They are harmless, and only taking advantage of a good spot. That good spot, happens to be diseased trees! This appears that it could be bacterial. General fungicides can, usually, help.