Immune mediated dermatitis

Question
I was hoping you might offer some insight into a recent experience. I lost an Australian Shepherd to a type of immune mediated or drug induced dermatitis, but the final diagnosis was never resolved.

The dog was female, seven years old, healthy, kept indoors, with no previous history of autoimmune or immuno-suppressed history in herself or direct lineage.

The first noted symptom was scabbing on the tips of her ears, followed by a scab on the juncture of the nose leather and muzzle. On the third day I noted a black, purulent discharge from her ears. The first visit to our regular vet came back with a diagnosis of fly bite dematitis on the ears and a possible ear infection. Antibiotics and a cream based repellent were prescribed. After a week, scabbing began to expand to her cheeks and around her eyes.

A return visit produced a preliminary diagnosis of Erythma multiforme and we were referred to a very well known specialist group in Houston.

All meds were discontinued and skin biopsies performed. Within a few days, the lesions had expanded even further and the skin began sloughing, blistering, and bleeding. Because of the sudden onset of the disease, a drug reaction was suspected, however there had been no change in her regime. She had not recently been vaccinated, she was in the middle of a month and so HW preventative had been given at least two weeks prior. She was on no other medications until her initial symptoms were diagnosed.

She showed elevated liver enzymes and as some lesions would heal, others would appear until about 20-25% of her body surface was affected. The legs, muzzle, ears and eyes had sloughed off most of the epidermal layer, leaving the bloody raw dermis beneath. Lesions began to form down her mouth and into her throat, requiring intraveous feeding for days at a time. As different antibiotics, steroids and pain medication were tried she would rally for a few days, but eventually continued her downward slide. Her medications included Cephlalexin, Prednisone, Enrofloxacin, Dexamethasone and Cyclosporin--each exchanged for another as their effectiveness wore off.

Although a biopsy was performed twice, I never did receive a final affirmative diagnosis. In just three short weeks, her continued failure to improve to any medication and her overall deterioration forced us to make the difficult decision to euthanize her.  

Some of the possible diagnosis were hepatocutaeous syndrome, EM, and TEN.

In light of the fact that she had no previous history of auto immune problems, was not given any new food or medications at the onset of the symptoms and the failure of the disease to abate despite fairly aggressive treatment, do you have any insight as to what may have happened to have caused this to occur?

I own six Australian Shepherds, breed and show. These dogs are like my family, sleeping on my bed, sharing my home with me and so this loss was devastating especially not knowing why it happened and if I could have done something different along the way.

Any insight you may have would be greatly appreciated.


Answer
I know of the group you refer to in Houston and they do an excellent job.  Dr. Beale, the dermatologist is world known and if she couldn't help you, then there must have been something very unusual.  If you did not get the biopsy results, I'm sure they would be happy to share these with you.

There are many diseases that just show up without any warning.  Unfortunately, this happened to your dog.  I cannot give you any more insight except to express my condolences.