I'm not sure. Just from the title 'hereditary a true story', it doesn't necessarily scream 'horror'. It could be a serious documentary - type story about heredity.
Mange can be hereditary. Certain breeds or lines of animals may carry genes that make them more susceptible. But it's not the only factor; other things like poor hygiene and contact with infected animals can also cause mange.
Yes, there is a possibility that demodectic mange is hereditary. Genetic factors can play a role, but other factors like the dog's immune system and environment can also contribute.