Leukemia in Dogs

Question: Dear Dr. Richards, My husband and I just subscribed last evening but have been visiting your website to learn about possible causes, medications, and effects that have been referenced in regards to our 10-year old Sheltie spayed female. In July 2000, she suddenly was stricken by something that caused her to have facial spasms, frequent shudders and weakness in her hind quarters where she fell to the floor on her side, straight down on all 4s or just her hind quarters. At first, the episodes came every 30 minutes and lasted very briefly but continued day and night and she paced for 24-hours. Then, they progress to every 15 seconds. Her only rest lasted no more than 90 minutes.

She's been to Auburn University Veterinary School where her neurologist took an MRI, CSF, CBC and tests for infectious diseases to find the root cause. All results came back normal. She was placed on phenobarbital, prednisone, doxycycline, trimethoprim-sulfa, sucralfate for seizure control (she had one full seizure the morning of her MRI), possible Rocky Mt. Spotted Fever and inflammation of her brain. She completed the doxycycline and trimethoprim but remained on phenobarbital (30 mg twice daily), prednisone (10 mg twice daily for 8 days then down to 10 mg once daily for 1 week then down to 10 mg once every other day), 1 g sucralfate 3 times daily. The neurologist offered 2 possible causes: distemper or stroke. Stroke was the less likely possibility since the onset of her problems progressively worsened over 2 weeks from mid-July to late-July. She's been current on all her innoculations since she was born in 1990 and only once missed her distemper vaccination in 1995. But we understand that batches of vaccines can sometimes be contaminated or be ineffective.

Although she wasn't her usual perky self, she was better without the spasms and shudders. She slept briefly in 2-3 hour stretches at night. Two weeks later, when she went in for her phenobarbital levels check, they were minimally within range. Then, she started to lose her toenails, her toe pads had open sores, a tiny spot appeared on each of her eyes (corneal), she became slightly anemic and her tongue turned black for a day and again for 5 days. Her prednisone was at 10 mg every other day, so she was adjusted back to 10 mg once daily. Her regular vet suggested changing her from phenobarbital to KBr, which I was glad to do with its fewer side-effects. I covered her feet with socks to prevent her chewing them, gave her baby aspirin for her tongue and started her on KBr for the next 5 weeks (where we are today).

Then we tried to reduce her prednisone again on September 09, 2000 to 10 mg once every other day. She became too weak to stand for more than 2 minutes. She was like this for 5 days and her gums became very pale. Of course, she was too weak to do anything but sleep...ironically, her first time for a full night's sleep. Since she was due for her KBr levels measurements in a few days, anyway, I called her regular vet to have her blood tests done and for her to be seen for the latest problems. Her KBr levels were barely within range and she was very anemic with an enlarged abdomen. An abdominal ultrasound was done showing an enlarged liver and spleen. The liver situation from her phenobarbital. The spleen was more of a concern (her 1997 radiographs indicated an enlarged spleen then). She also had a urinary tract infection with traces of blood in her urine. She was given epogen injection for her anemia and amoxi 250 mg for her infection. Her regular vet recommended we return to Auburn.

This week our dog was admitted back to Auburn where she remains. She's being examined and watched by Internal Medicine. Tests of her blood showed low counts of mature white blood cells and low count of red blood cells. There's a proliferation of immature white blood cells. She was running a fever, too. Her liver, spleen and bone marrow were aspirated. She underwent another ultrasound on her abdomen. Her spleen was free of tumors although there are nodules. Her lungs looked clear. Her heart sounds fine. The aspirations of her liver and bone marrow showed presence of the immature white blood cells. The bone marrow showed too many of them that crowded out mature white and red blood cells. Her spleen aspiration looked fine. She was given a growth factor for her bone marrow and her red blood cell count very minimally increased. The internal medicine doctor believes she has acute leukemia. The only other possibility would be a viral attack on her bone marrow. He's taking a biopsy of her liver today to confirm the presence of immature white blood cells.

Our dog's case is puzzling Auburn. The neurology, oncology, pathology and internal medicine departments are all involved in her case this week. She's receiving growth factor daily, now, to boost her mature white blood cells. Her red blood cells remains low at 20%, but the internal medicine doctor hopes that will improve as the mature white blood cells start to increase and she's able to fight off infections on her own. Along with her prednisone (5 mg twice daily), phenobarbital, KBr, sucralfate, and amoxicycline, she's getting another antibiotic and growth factor.

Lupus has been ruled out. I've asked for a babesiosis test to be done and test results won't return from Louisiana University until next week about the same time pathology results on her liver biopsy will return.

It seems that leukemia is rare in dogs. We find no mention of it on your website. A couple of other veterinary websites we've visited discuss leukemia. However, since your explanations are more in plain English, could you explain the condition to us, please? We know that there are 2 types: acute and chronic. Chronic has better prognosis due to its slower onset and progression. Could there be any relationship between her early neurological symptoms and to her present anemic symptoms?

Thank you! N. & S.

Answer: N & S -

I think that leukemias are pretty uncommon and that it is probably also likely that they do not get diagnosed as often as they occur, since the clinical signs associated with leukemias can be very variable and are easy to confuse with other disorders.

There are several kinds of white blood cells that make up the immune system. The most common one is the neutrophil, followed by lymphocytes, eosinophils, monocytes, basophils and some variants of these cells. Each of these is produced by a group of precursor cells in the bone marrow that are referred to as stem cells. The stem cells differentiate and produce the different types of white blood cells but they arise from the same basic cell line, so there are often mixed types of leukemias.

Leukemia is the presence of cancer cells in the bone marrow itself. This is different from lymphoma, the other common white blood cell cancer, because lymphoma arises from tissues outside the bone marrow, such as lymph nodes or the spleen. There are two forms of leukemia, acute and chronic. The acute form usually has poorly differentiated stem cells, produces anemia, drops in white blood cell count and a lot of secondary problems associated with anemia and a severely deficient immune system. When bone marrow is examined, acute leukemia usually causes the bone marrow to have a large number of cancer cells, making up at least 30% of the bone marrow cells. The chronic form of leukemia is different in that it is usually possible to identify the type of cell that is proliferating, such as granulocytic (neutrophil) leukemia, lymphobastic leukemia, eosinophilic leukemia or lymphoid leukemia. White blood cell counts are usually elevated and sometimes are extraordinarily high, such as 100,000 to 300,000 wbcs/ul. Clinical signs tend to be non-specific for this disorder, too but enlarged lymph nodes and spleen, weakness, lethargy, lameness, fevers, increased drinking and urinating, bleeding disorders, liver enlargement and pale gums have been reported to occur.

The prognoses for acute lymphoblastic leukemia and for acute nonlymphoid leukemia are both very grave, with most affected pets living only a short time after it is possible to make a diagnosis of these conditions, even with treatment. There is no consistently successful treatment plan that I know of but l-asparaginase (Elspar Rx) was supposed to be helpful in some cases. This medication is not currently available, as far as I know, though.

Chronic lymphocytic leukemia and chronic nonlymphoid leukemias have a better prognosis, although there isn't sure treatment for them, either. Some dogs are reported to live for months, to years, with these conditions. I think that the majority of patients probably do well for the shorter time period, though.

It is good that your sheltie is at one of the veterinary schools because there are resources there for confirming the diagnosis and for obtaining the most current therapeutic information.

I do not know how frequently neurologic signs, such as seizures, are associated with leukemias, but it they are listed as one possible symptom in Ettinger and Feldman's "Textbook of Veterinary Internal Medicine". At the present time, I do not think that initiating factors for leukemia have been identified in dogs, so there may easily be a link between the neurologic symptoms and the leukemia, if it is present, but it would be hard to be sure.

I wish that I could help with this situation but you are doing the right things and have the help of people far more expert than I am in this kind of care.