Coral bark maple (Sango Kaku) and other colored bark Japanese maples are extremely prone to a bacterial blight, Pseudomonas syringae. But that most often affects newer growth with blackened dieback of exterior shoots. If it appears lower on the limbs or trunk or the interior of the tree, there is minimal chance of long term survival. I can't see clearly from the photos if this may be a factor or not.

Otherwise, I'd wonder what sort of cultural practices you have been following. Last year was a pretty severe drought year for parts of the east coast. How was watering handled? Can you show a photo of where the trunk enters the ground?

btw, if your tree recovers from whatever is ailing it, it is planted far too close to the house. Full size Sango Kaku (there are dwarf coral barks as well) can easily develop a 20-25' canopy spread.

Thank you! I will take some more photos this afternoon and update my post!