Iguana tail problems. Help!

My female iguana is about 4 years old and for the past year she's had trouble shedding on the center of her tail. It turned black and then became very dry and brittle. Now it has big cracks in it that appear to be quite deep. Sounds like dry gangrene however that usually starts at the tip and the tip of her tail and a few inches upward are fine. I am making a vet appy tmrw as it has gotten
much worse. Any opinions are welcome. I have a pic but have no idea how to attach it from my iPhone.