Cats weight loss

Anemia, Weight Loss, Eating Litter, Lethargy, Allergy. FLV/FIV Negative. Autoimmune Disease? My cat, Tux, is a 3 years old domestic short-hair male cat. He was a normal healthy kitty except he always had an extra appetite and quickly reached 20 lbs. Sometimes I noticed him licking traces of litter off the carpet or near the litter box but I never made anything out of it.

About 9 month ago out of nowhere he got anophylactic reaction, his airways got swollen, he had foam coming out of his mouth, and he had trouble breathing. We rushed him to the hospital where they stabilized him but couldn’t tell us what caused it. Then he was fine for the next 6 month until it happened again in November.

By that time we moved from California to New York so we were in the different apartment and in the different environment. He had to go to the animal hospital nearby, get steroids and extra oxygen. We had him see a vet specializing in dermatology/immunology who did allergen testing but it came back positive for just about everything, including cat hair! The vet prescribed hydroxyzine and accolade.

He's been fine until about 3-4 weeks ago when he became lethargic, lost his appetite and experienced weight loss. We stopped giving him medications but he didn’t get back to his normal state. He has been hiding in the closet or a dresser drawer, staying there all day, not moving much and not eating much. So we took him in to the vet again. Unfortunately, he was found to be severely anemic with an enlarged spleen, needed a blood Transfusion and had a bone marrow biopsy.

The results of his bone marrow biopsy just came back today but it's inconclusive. They don't see obvious leukemia but see hypo-cellular erythrocytes and hyper-cellular lymphocytes. The pattern of his macrocytic anemia was concerning for Feline Leukemia Virus, however, his serum testing for FLV was negative twice! He is also negative for FIV.

Anyhow, the vet thinks it's either FLV with false negative blood results or an autoimmune condition. She's recommending to repeat his bone marrow biopsy and send it for direct testing of FLV (cannot be done on his old specimen as it must be fresh). Alternatively, we could start treatment with high dose steroids but at a risk of him getting worst if it's FLV. Tux always had somewhat bold spots from above his eyes to his ears symmetrically on both sides but recently it seemed like he lost more hair in that area.

He also has a very rare type B blood. He has weight loss of 4 lbs already and is not getting better. Has anyone had a similar situation with their cats weight loss? We have already spent over $5,000 and can’t afford to spend more money but the mystery remains. Thank you.