If you've recently noticed an increased resistance to exercise and a tendency to lay around on the part of your dog, then he or she might very well be the victim of a phosphofructokinase deficiency.
Phosphofructokinase deficiency is a disease that inhibits the body from metabolizing glucose into usable energy, leading to the aforementioned lack of enthusiasm and pep that can seem to strike without warning. In advanced stages, the disease can even lead to the onset of more advanced muscular diseases and destroy red blood cells, which can lead to anemia.
Symptoms of a phosphofructokinase deficiency are numerous. First of all, your dog will seem to suffer from sudden and unexplained episodes of exhaustion and during these times will resist even the simplest forms of exercise that he or she might usually be ecstatic about, such as going on walks. These periods are also marked by a characteristic muscular weakness; you might find that your dog is no longer able to perform tasks like going up and down stairs as easily as he or she once could. Their mucous membranes (nose and gums being the most obvious) will take on a pale yellow appearance, as if jaundiced, and at times they can even begin to run a high fever. While all of these symptoms should be taken seriously and treated as soon as possible, there is one symptom that ought to be taken as an emergency situation. If your dog's urine takes on a brown color while coupled with the aforementioned symptoms, veterinarian attention should be sought at once or you risk more serious organ damage to your dog's kidneys.
Your veterinarian will attempt to diagnose phosphofructokinase deficiency by observing the dog over a period of time, and taking a series of blood samples to monitor the level of his or her anemia. Prolonged intolerance for exercise as well as fever and muscular wasting due to inactivity are also tell-tale signs. While these could easily be symptoms of other problems, there does exist a very specific test for phosphofructokinase deficiency that can instantly rule out any other causes with a single blood sample.
Generally, there is no treatment for this disease, but it has no real adverse effect on a dog's lifespan if properly managed. Management consists of ensuring that your dog gets plenty of exercise in between bouts of the disease and that he or she avoids any undue stress. In addition, owners of pets with phosphofructokinase deficiency should be educated about the signs and symptoms that go along with the disease so that they can begin to accurately predict and forestall outbreaks. During particularly bad instances where your dog simply seems to have no energy at all, he or she might be treated with nutritional supplements in the form of intravenous feeding tubes. Again, while this might have the appearance of a drastic treatment, the disease is not usually very serious.
Because this is a hereditary disease, affected animals should not be bred.