Chronic lymphocytic leukaemia in dogs (CLL)

Chronic lymphocytic leukaemia is a type of cancer that affects the white blood cells or lymphocytes of the body, which are in turn a part of the body’s immune system. This form of cancer or leukaemia is thankfully reasonably rare in dogs, but it is also very serious, with a reasonably poor long-term prognosis for affected dogs in most cases.

Chronic lymphocytic leukaemia or CLL also tends to develop slowly and subtly, with hard-to-spot symptoms that mean that the condition is already often quite advanced by the time diagnosis is made, which further complicates treatment.

In this article, we will look at CLL in dogs in more detail, including how and why it develops, what sort of dogs are most at risk for the condition, how to identify the symptoms of the condition, and what treatment and management options are available for affected dogs. Read on to learn more.

What is chronic lymphocytic leukaemia?

CLL or chronic lymphocytic leukaemia causes mature lymphocytes – a certain type of white blood cells that form part of the immune system – to build up in the spleen and bone marrow itself. This causes higher than normal levels of lymphocytes circulating and present within the body, which leads to enlargement of the lymph nodes and spleen, as well as potentially anaemia and a low blood-platelet count.

Why do dogs develop CLL?

The exact trigger or root cause for CLL in dogs is unknown, and no formal connection has been made between development of the condition and a hereditary cause. However, CLL does seem to be more prevalent across certain breeds and types of dogs than others, which indicates that there may be a genetic mutation or hereditary anomaly in play that causes or contributes to development of the condition.

The DNA structure of the cells in the body of affected dogs undergo a measurable change as the condition develops, and so it is possible that future research will isolate a specific gene or gene mutation that causes the condition and so, enable a testing protocol to be introduced to identify a hereditary predisposition to CLL in canine bloodlines.

What sort of dogs are at risk of the condition?

Any dog can potentially develop CLL, although it tends to be diagnosed in mature and elderly dogs more commonly than their younger counterparts, and affects male dogs at a higher rate of prevalence than females.

Small and toy dog breeds of all types tend to be more at risk than medium and large breeds, although the German shepherd, a large breed itself, also seems to present with more cases than average across the entire canine population.

The symptoms of chronic lymphocytic leukaemia in dogs

Spotting the symptoms of chronic lymphocytic leukaemia in dogs can be very challenging, because the condition is slow to develop and often, asymptomatic, meaning that affected dogs have often reached quite a long progression of the disease by the time it is formally diagnosed.

Even if your dog does display symptoms, pinpointing them to CLL can be challenging for even experienced vets, and will generally require a differential diagnosis to be performed to consider and rule out other potential illnesses that present with similar symptoms.

In dogs that are displaying symptoms of CLL, some of the following anomalies may be present, some of which you can keep an eye out for at home and others that may not become apparent without veterinary investigation:

• Drinking more water than normal and being very thirsty.
• Needing to urinate more frequently as a result.
• Enlarged lymph nodes.
• An enlarged spleen.
• A slightly elevated temperature.
• A tendency to bruise easily, and bruising more dramatically than a minor injury would usually cause, as well as bruising taking longer to heal.
• Slightly decreased appetite, activity levels, and alertness.
• Blood testing will reveal a low red blood cell count, lower than normal platelet count, and high levels of lymphocytes in the blood.

Diagnosis and treatment

Diagnosis of CLL is often delayed until the dog is quite ill and symptoms quite pronounced, because the condition is usually largely asymptomatic. If you own a mature or elderly dog, it is a good idea to schedule a full senior health check and blood workup once your dog enters old age, in order to get some baseline figures for your dog’s health and pick up on any abnormalities – which can help to ensure an early diagnosis in the case of problems.

Diagnosis of CLL is made by means of blood and urine analysis, bone marrow evaluation, and potentially, X-ray and ultrasound examination too.

Because CLL is a systemic cancer, it cannot be surgically removed from the body, and so treatment of the condition usually means chemotherapy courses and blood cell count monitoring to put the cancer into remission and correct some of the symptoms.

However, chemotherapy rarely results in a total reversal of the condition or effects a cure, and affected dogs will usually succumb to the chronic lymphocytic leukaemia at some point. Chemotherapy can extend the dog’s viable lifespan and improve their quality of life, often for several years, and so this is certainly a viable option to consider in terms of managing the condition for the long term.