Foxy (dog) skin irritation

Foxy, my mom's dog, has some type of issue on her skin. The affected area on middle upper back has a scabby area. Not due to being scratched at or bitten up by her as she can't reach. If anyone knows what it is, how to fix it, or could help with the vet we would be greatful! Any assistance would be greatly appreciated! Thank you for your help!