What Causes Itching And Discolored Patch Below The Shoulder Blade?

Hi Doc! Just want to now about a discolored patch below my shoulder blade that itches once in a while and for me to get to it I have to use some kind of hair brush to scratch it. It turns red after I scratch it and then I get a slight burning sensation there. After it goes away. Comes back now and then. I've had it for years. What do you think it could be.