For a few years, our Liberty apple has developed tiny pouches on its leaves. Soon, the leaves turn yellow and drop prematurely. It also seems to affect the developing fruit with dimpled dark spots.
It sounds like your tree has apple blister mites, a type of eriophyid mite. They are tiny, and you would need a magnifying lens to see them. There is information about this mite in the Pacific Northwest Insect Management Handbook, including life cycle, and methods of control with dormant sprays (some of which are accepted for use in organic orchards). The mites overwinter under the outer bud scales on the tree. In case you are wondering where to look for bud scales, when the tree loses its leaves in fall or winter, bud scales form at the ends of branches or stems. The bud scales protect new growth that will emerge here. When buds swell in spring, the mites will burrow into them to feed. Once the blossoms have fallen, they will progress to leaves and developing fruit.
Mites are attracted to drought-stressed trees, and to nearby weeds like clover, mallow, bindweed, and knotweed. They can be carried from tree to tree by wind or birds and other insects. Usually, ample rain and cold winter weather keep mite numbers down, but as the climate changes, we may be creating conditions that are more favorable to them.
You might be able to find a source for predatory mites to help control the blister mites. Washington State University’s Tree Fruit research site describes several species of phytoseiid predatory mites.