So reticulocytes (immature blood cells) were normal? White blood cell count was normal?
There really are a million things that can cause anemia. Our Tuxie started eating litter (a sign of anemia - but our vet didn't know that at the time, as some cats eat litter and are not anemic). He was tested for leukemia - always the initial concern. When that came up negative, they progressed through the diseases, including tic born diseases. Everything turned up negative.
After calling around to the country's specialists, our vet decided to treat it like he would feline hemolytic anemia, an autoimmune disease. In the meantime, he received a blood transfusion (though cats can usually receive only one - their blood is far more complicated than human blood, and after the first transfusion, when introducing another "new" blood into their little bodies, they usually send out some type of antibodies that cause the blood to coagulate, thus it cannot be transfused
), and shots of Epogen (to boost his red blood cell count) and he also needed Nupogen (to boost his white blood cell count). He was given prednisone (a steroid) to suppress his immune system. This worked - at first. His blood cell count would go up - and then down again.
We fought for two years. We got to a point where his PCV was 7%. He was so anemic he was soooo out of it - he'd walk up to his food bowl and just look at it. It was so difficult to get him to eat. The vet said he had a few days, and that he was out of bullets. My hubby was in hysterics. That's when the vet tried depomedrol instead of prednisone. Thank God it worked!
Our Tuxie needed shots every day - then every two days, then every week. We were at the vet so frequently we actually moved so our drive would be 1/2 hour less for our kitty.
This went on, like I said, for two years.
He was worth every penny we spent. The time needed between shots of depomedrol got longer and longer, and has been about every 3 months for the past year and a half.
He is our alpha kitty, bounding around here like Tigger, or racing around like Ricochet Rabbit.
Anemia is often very treatable, so learn as much as you can, and get involved in that blood chemistry - and keep your eye on your kitty. Watch the color of his gums and watch for him becoming tired more easily, eating less, or becoming listless. And if your vet doesn't seem to be searching hard enough for answers, get a second opinion.
Sending vibes to your kitty! I hope it's something easily diagnosable and easy to treat!