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Thrombocytosis in dogs
A D VA N C E S
PAG E 3
THROMBOCYTOSIS IN DOGS Background Thrombocytosis is an excessive platelet concentration. Thrombocytosis is generally defined as a platelet count greater than 500,000/μl. Platelet counts greater than 1,000,000/μl are considered extreme thrombocytosis. It can be classified as either primary or secondary in origin. Primary (essential) thrombocytosis, is a myeloproliferative disease. Secondary (reactive) thrombocytosis is caused by an underlying disorder, such as inflammation, neoplasia, or iron-deficiency anemia. Secondary thrombocytosis occurs more
PAG E 4
A D VA N C E S
frequently than primary thrombocytosis. Reactive thrombocytosis may result from overproduction of one or more of the thrombopoietic factors, such as interleukin (IL)-6. In inflammatory conditions, IL-6 is a major stimulatory factor in thrombopoietin production. Excision of the spleen, a regulator of platelet numbers, can cause transient thrombocytosis. Some hormones and drugs can also cause thrombocytosis. Epinephrine release causes splenic contraction which can then produce a transient increase in platelet numbers. Hyperadrenocorticism and glucocorticoid administration have both been associated with thrombocytosis in dogs, as has vincristine administration. The diseases and conditions associated with thrombocytosis in dogs need greater clarification.
(18). Marked (850,000 to 969,000 platelets/FL) or extreme (at least 970,000 platelets/FL) thrombocytosis occurred in 24 (14.5%) dogs. Twelve dogs (50.0%) had neoplasia. Thromboembolism occurred in 13 (7.9%) dogs.
Objectives
Editor Annotation
To characterize diseases and conditions associated with thrombocytosis in dogs.
These authors went over records of their teaching hospital and found 4 to 5% of dogs presented had thrombocytosis with platelet levels of greater than 600,000/μl. Some clinicians are concerned about thrombocytosis at lower values than the criterion utilized by these authors and will consult with a clinical pathologist or internist. This study is beneficial to help direct the clinician toward certain diseases. Primary thrombocytosis was not identified in this study. All cases were secondary to another disease. The most common associated disease was neoplasia, and the highest or most extreme thrombocyte counts were also associated with cancer. This observation is consistent with what has been noted in humans and cats. Reactive thrombocytosis was observed most commonly following glucocorticoid and/or antineoplastic agent therapy. Thromboembolism appears to be a rare complication of thrombocytosis, but it is more common in dogs than humans. There is still a lot more to learn about thrombocytosis and the mechanism for occurrence. The next time you identify this abnormality on a hemogram, look closely for any potential neoplastic process. Also be cognizant of a potential rebound thrombocytosis in cases of chemotherapy or when treating immunemediated diseases, such as thrombocytopenia or hemolytic anemia. (LDM)
Procedure A retrospective search of dogs presented for examination in a 1-year period was conducted for dogs with thrombocytosis (platelet count greater than 600,000/μl) and complete medical records during a 1-year period. Breed, gender, age, hemogram results, alkaline phosphatase and gamma-glutamyltransferase activities in some dogs, administration of glucocorticoids or vincristine, and the primary diagnosis were evaluated.
Results Thrombocytosis was found in 240 of 5,342 dogs (4.6%), and 165 (3.1%) met inclusion criteria. Thrombocytosis was secondary in all dogs. Underlying diseases and conditions were neoplasia (56, 33.9%), inflammation (55, 33.3%), miscellaneous disorders (26, 15.8%), neoplasia plus a second disease (13, 7.9%), endocrine diseases (8, 4.8%), and multiple diseases (7, 4.2%). In dogs with neoplasia, carcinomas (24) and round-cell neoplasms (20), especially lymphoma and mast cell tumor, were the most frequent tumors. Inflammatory disorders consisted of immune-mediated disorders (11), neurologic diseases (8), infectious diseases (6), allergic disease (5), orthopedic diseases (4), gastrointestinal diseases (4), and miscellaneous conditions (17). Of the 165 dogs, 73 (44.2%) had received glucocorticoids (55) or vincristine
Author Conclusion Thrombocytosis in dogs occurs most frequently secondary to neoplastic and inflammatory diseases and was commonly associated with glucocorticoid and vincristine administration. Thromboembolic complications occurred in a small number of patients. Marked or extreme thrombocytosis was more likely to occur with neoplasia than with other conditions.
Inclusions One figure, 1 table, 29 references.
Neel JA, Snyder L, Grindem CB. Thrombo-
cytosis: a retrospective study of 165 dogs. Vet Clin Pathol 2012;41:216-222.
PAG E 3
THROMBOCYTOSIS IN DOGS Background Thrombocytosis is an excessive platelet concentration. Thrombocytosis is generally defined as a platelet count greater than 500,000/μl. Platelet counts greater than 1,000,000/μl are considered extreme thrombocytosis. It can be classified as either primary or secondary in origin. Primary (essential) thrombocytosis, is a myeloproliferative disease. Secondary (reactive) thrombocytosis is caused by an underlying disorder, such as inflammation, neoplasia, or iron-deficiency anemia. Secondary thrombocytosis occurs more
PAG E 4
A D VA N C E S
frequently than primary thrombocytosis. Reactive thrombocytosis may result from overproduction of one or more of the thrombopoietic factors, such as interleukin (IL)-6. In inflammatory conditions, IL-6 is a major stimulatory factor in thrombopoietin production. Excision of the spleen, a regulator of platelet numbers, can cause transient thrombocytosis. Some hormones and drugs can also cause thrombocytosis. Epinephrine release causes splenic contraction which can then produce a transient increase in platelet numbers. Hyperadrenocorticism and glucocorticoid administration have both been associated with thrombocytosis in dogs, as has vincristine administration. The diseases and conditions associated with thrombocytosis in dogs need greater clarification.
(18). Marked (850,000 to 969,000 platelets/FL) or extreme (at least 970,000 platelets/FL) thrombocytosis occurred in 24 (14.5%) dogs. Twelve dogs (50.0%) had neoplasia. Thromboembolism occurred in 13 (7.9%) dogs.
Objectives
Editor Annotation
To characterize diseases and conditions associated with thrombocytosis in dogs.
These authors went over records of their teaching hospital and found 4 to 5% of dogs presented had thrombocytosis with platelet levels of greater than 600,000/μl. Some clinicians are concerned about thrombocytosis at lower values than the criterion utilized by these authors and will consult with a clinical pathologist or internist. This study is beneficial to help direct the clinician toward certain diseases. Primary thrombocytosis was not identified in this study. All cases were secondary to another disease. The most common associated disease was neoplasia, and the highest or most extreme thrombocyte counts were also associated with cancer. This observation is consistent with what has been noted in humans and cats. Reactive thrombocytosis was observed most commonly following glucocorticoid and/or antineoplastic agent therapy. Thromboembolism appears to be a rare complication of thrombocytosis, but it is more common in dogs than humans. There is still a lot more to learn about thrombocytosis and the mechanism for occurrence. The next time you identify this abnormality on a hemogram, look closely for any potential neoplastic process. Also be cognizant of a potential rebound thrombocytosis in cases of chemotherapy or when treating immunemediated diseases, such as thrombocytopenia or hemolytic anemia. (LDM)
Procedure A retrospective search of dogs presented for examination in a 1-year period was conducted for dogs with thrombocytosis (platelet count greater than 600,000/μl) and complete medical records during a 1-year period. Breed, gender, age, hemogram results, alkaline phosphatase and gamma-glutamyltransferase activities in some dogs, administration of glucocorticoids or vincristine, and the primary diagnosis were evaluated.
Results Thrombocytosis was found in 240 of 5,342 dogs (4.6%), and 165 (3.1%) met inclusion criteria. Thrombocytosis was secondary in all dogs. Underlying diseases and conditions were neoplasia (56, 33.9%), inflammation (55, 33.3%), miscellaneous disorders (26, 15.8%), neoplasia plus a second disease (13, 7.9%), endocrine diseases (8, 4.8%), and multiple diseases (7, 4.2%). In dogs with neoplasia, carcinomas (24) and round-cell neoplasms (20), especially lymphoma and mast cell tumor, were the most frequent tumors. Inflammatory disorders consisted of immune-mediated disorders (11), neurologic diseases (8), infectious diseases (6), allergic disease (5), orthopedic diseases (4), gastrointestinal diseases (4), and miscellaneous conditions (17). Of the 165 dogs, 73 (44.2%) had received glucocorticoids (55) or vincristine
Author Conclusion Thrombocytosis in dogs occurs most frequently secondary to neoplastic and inflammatory diseases and was commonly associated with glucocorticoid and vincristine administration. Thromboembolic complications occurred in a small number of patients. Marked or extreme thrombocytosis was more likely to occur with neoplasia than with other conditions.
Inclusions One figure, 1 table, 29 references.
Neel JA, Snyder L, Grindem CB. Thrombo-
cytosis: a retrospective study of 165 dogs. Vet Clin Pathol 2012;41:216-222.