Mystery Illness

Good morning, My 7 year old female frenchie has been chronically unwell for almost 1 year, she was previously very healthy. She has recurrent UTI's (often culturing E-coli), weightloss, hairloss, reduced exercise tolerance, muscle wastage, increased thirst (3x more than normal) and extensive calcinosis cutis (some of which are errupting as lesions), very dilute urine. She has the appearance of a Cushingoid dog but 2 low dose dex tests have come back as negative for Cushings. Her thyroid is normal, bloods are normal (slightly elevated LFT), abominal ultrasound was normal, she has had skin biopsies that just showed the Calcinosis cutis, lymph node biopsies were normal, other lumps confirmed to be fatty tissue. 2 weeks ago she had a large abcess on her neck thought to be caused by another calcium deposit. The vet is considering diabetes insipidus and a 3rd low dose dex test if a urine cortisol creatinine ratio comes back as positive. She had had 2 of these before as well. I'm hoping maybe someone has seen symptoms like these before and can offer some advice? My vet is very good and she is also doing her own research but we have now spent thousands on the tests and we are still at square one. Thank you for taking the time to read this post.

Hello!  - and I'm sorry to hear that your dog is what we call, an 'interesting case.'  As a vet, when I cannot come up with more explanations for a clinical picture (i.e. the lab results and examination I have seen), I sometimes call my local laboratory for information, as pathologists are a mine of useful information.  Your vet may already be taking this approach.  Obviously they are likely to have a better handle on such a case than I can get here; my understanding is that Calcinosis Cutis can occur in cancer, or complications relating to the adrenal gland (such as Cushings or Addisons), or in rapid fat breakdown.  A pathologist my well advise your vet as to what to do next in terms of diagnosis.   Some breeds have a genetic tendency. Please will you let us know if you find out?