Top 5 Breed-Associated Hematologic Abnormalities

Heather A. Kridel, DVM, DACVP (Clinical), IVG Hospitals by Ethos, Woburn, Massachussetts

ArticleLast Updated October 20165 min readPeer Reviewed

Hematologic evaluation via CBC—including automated analysis and manual blood smear evaluation—is routine for wellness health screening and diagnostic evaluation in clinically ill patients. Observed abnormalities typically indicate an underlying disease process; however, many breed-associated hematologic anomalies are not associated with clinical disease. These takeways are important to avoid misdiagnosis of pathologic disease processes.

1. Inherited Macrothrombocytopenia in Cavalier King Charles Spaniels

Autosomally inherited macrothrombocytopenia is common in Cavalier King Charles spaniels.1 One study reported either homozygous or heterozygous mutations in the gene that encodes ß1-tubulin in 81/100 Cavalier King Charles spaniels.1 Affected (ie, homozygous) dogs typically exhibit a decreased total platelet count ranging from 30 000 to 100 000/µL; carrier (ie, heterozygous) dogs exhibit a platelet count from ˜100 000 to 250 000 (range, 200 000-500 000/µL).2 Thrombocytopenia in heterozygous and homozygous dogs, however, is not associated with clinical bleeding, likely because the platelet function is normal and total platelet mass (ie, plateletcrit) is not decreased.2,3 

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Macrothrombocytes are platelets that are as large as or larger than erythrocytes in diameter (Figure 1).2 Because automated hematology analyzers that use impedance technology cannot distinguish these large platelets from erythrocytes, the automated platelet count may be much lower than the actual count. Performing a platelet count via hemocytometer or a platelet estimate on a blood smear may be more accurate for evaluation of true platelet count. It is important to recognize this breed-associated abnormality so these patients are not presumed to have thrombocytopenia associated with more severe underlying disease (eg, immune-mediated thrombocytopenia).

Featured Image
FIGURE 1

Peripheral blood smear from a Cavalier King Charles spaniel with macrothrombocytopenia. A macrothrombocyte (arrow) is present among erythrocytes. Wright-Giemsa, 100× original magnification

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