Billie, is a 4 year old, spayed female Australian Shepard that presented to us 2 weeks ago. She has a very astute owner who happened to notice while they were playing at the dog park that blood was accumulating in the iris of Billies' eyes. This was a very subtle thing to notice and we commend Jen for her observation skills!
Because it was late on Sunday afternoon, Jen took Billie in to clinic where a CBC and general blood profile were run. It was determined that Billie had almost no platelets and that her coagulation profile was increased. This was the reason why blood was beginning to leak into the iris of the eyes. It was also noted that Billie had begun to loose small amounts of blood into her the skin of her belly and in the gums of her mouth. These very small bruises are called petechiae.
So, what are platelets and why are they so important? Platelets are cloud shaped blood cells that are not related to red blood cells or white blood cells. Their primary function is to float around in the blood stream until they find damage to a blood vessel. When this is detected they will bind to the damaged blood vessel and to each other forming a plug to stop the vessel from bleeding. Blood vessel damage can occur as a result of normal wear and tear or in some instances to trauma. Platelets are generated and released into circulation from the bone marrow and generally live in the circulation 7-10 days in the dog. (In a human the platelet lives approximately 6-8 days.) At any given time, there are approximately 200,000 - 500,000 platelets normally patrolling the bloodstream for vascular damage. 20,000 - 50,000 platelets are considered to be the bare minimum to prevent spontaneous bleeding. So now it is understood why Billie was leaking blood into the iris, skin and gums.
Dramatic reductions in platelet numbers is almost always caused by an immune mediated response. However, intoxication from rat poisoning, tick-borne blood parasites or tumors, for instance, could lead to dysfunctional platelets. In many cases, the exact cause for this particular issue is never found.
In an immune mediated destruction of platelets, the immune system which normally recognizes the proteins on platelets as self begins to recognize the platelets as invading or "non-self" proteins. The immune system responds by generating antibodies against these "enemy shapes" and thus there is a destruction of the normal platelet.
Because Billie's condition was identified so early in the disease process she had not yet become anemic (an abnormally low red blood cell count). She was given the appropriate treatment and is well on her way to recovery.
Her only issue now is that she has to be kept quiet and on "bed" rest. She has never shown any signs of lethargy or depression and does not understand why she must be on rest. Last weekend she had green stools and Jen became very concerned that she might be eating rat poison though she has never used this. Rat poison is a green-blue color and often discolors the stools if eaten in large amounts. Upon further investigation she found out that Billile was protesting her "bed rest" orders.....she had torn to pieces and evidently eaten a green file folder! We decided to let her start having more freedom since she is doing so well!