Lyme, Addisons, Cushings?

Question
My 13 year old dog Kasey has been examined by our vet after suffering from a loss of appetite, some vomiting and general lethargy.  All of his bloodwork came back OK except for some elevated liver enzymes, low platelets and a positive result for lyme disease.  He has been getting the lyme vaccination since he was a pup.  Our vet is also suggesting testing for Addision's and/or Cushings, because he is also drinking excessive amounts of water and his coat has become dull and flaky.  I'm not sure what to think.  Could the lyme disease be a false positive if he's been getting the vaccination?  He seems to have symtoms all over the place and the vet can't pinpoint what the problem is.  Where do the symptoms of these three diseases overlap?  What would our next step be?  More bloodwork?  I'm not sure what I should be asking the vet.  I would appreciate some direction.
Thank you

Answer
The Lyme disease is most likely causing the low platelets and general lethargy.  Did the bloodwork show any evidence of anemia?  If so, I would be very concerned about an auto-immune condition.

I normally treat for 6 weeks with antibiotics for the Lyme Disease.  The Lyme vaccination is NOT 100% effective and dogs can still become infected about 10-15% of the time, but tend to show less disease symptoms than unvaccinated dogs.  

If your vet used the 3DX test from Idexx then a positive is an active infection...if titers were done you could get a false positive because of the vaccine--a western blot must be done to determine between vaccine and natural infection.

Lyme disease can cause increased thirst if spiking a fever or if affecting the kidneys...I would recommend checking a urine sample to look for protein loss and first signs of kidney disease in association with Lyme will lead to proteinuria (especially albumin detected on ERD test).  And you also want to rule out UTI.

I would give the antibiotics and then recheck the liver values.  If the ALKP is elevated with increased thirst and urination, then have a low dose dex. suppression test to check for Cushings.  Addison's will lead to an imbalance of sodium and potassium on bloodwork and animals can not handle stress (no adrenalin=steroid) and are lethargic and underweight.  Addison's is the opposite of Cushings (too much steroid in the system).  Addison's is more common in younger dogs.

An x-ray of the abdomend and chest would be a good idea, since Kasey is older, to check the size of the liver and look for any tumors.

I would also have the THYROID checked as hypothyroidism can lead to a poor hair coat, tiredness and seeking heat.

For specifics on each of the diseases, you can visit my website at www.antietamvet.com and look them up in the encyclopedia.