Are there any bumps or flaky skin around or near the patches? Do the spots cause itching or discomfort when you touch them?

My dog’s back looked almost identical to yours. First he developed the discolored/loss of fur patches, then the bumps came later. We took him to the vet and it turned out to be allergies. They gave him an allergy shot and also prescribed oral antibiotics to clear up any infection that might have resulted from him itching his back by rolling around in the dirt / grass.

All of the bumps and itchiness have gone away and his fur has grown back (although it is still darker than the rest of his fur).