I have a 7 year old Golden Retriever male. Approxiamtely 16 weeks ago he started to have a mucousy nasal discharge, occasionally tinged with dark blood. The dog was treated with antibiotics with minimal improvement. A swab was taken and showed positive for fungus. He was started on an antifungal agent and had a 6 week course of this. Then he received another 2 week course of antibiotics. There was never any real improvement in the discharge. About 2 weeks ago, he had a fairly significant nose bleed that did stop on its own. Was treated with oral ivermectin in case he had nasal mites. Following the treatment with ivermectin, he had another nose bleed and then sneezed out a fairly large piece of debris. Our vet examined the debris and felt it was fecal matter. Then, this past Monday, he had a severe nose bleed that would not stop. Tuesday he was admitted to the Alta Vista Animal Hospital in Ottawa and a rhinoscopy was done today. No masses were found, his sinus are okay, they saw what they think is a polyp at the back of his nasal cavity which was biopsied. Chest x-ray was clear. Both nasal passages are described as being abnormal and had a large amount of dark black/brown debris in them. This was removed and will be sent for histology/pathology. A skin biopsy was done on an area above his nose where he is losing pigment.
Has anyone ever had similar experiences? It seems that even the vets at Alta Vista are stumped by this boy. An input or ideas would be greatly appreciated.

Sounds like it may be caused by aspergillus fungus -- read this site, or do a Google search for more info, and see if you think it fits?
http://lowchensaustralia.com/health/aspergillosis.htm