*Every Cavalier owner should print out this article and take a copy to their veterinarian as many,
if not most, are not aware of this condition in Cavaliers.
 

Platelets in Cavalier King Charles Spaniels

W. Jean Dodds, DVM
HEMOPET
938 Stanford Street
Santa Monica, CA 90403
(310) 828-4804;FAX (310)-828-8251
www.hemopet.org;  hemopet@hotmail.com 

Healthy members of this breed often show low circulating platelet counts and can have large platelets that sort outside the platelet "window" of automated platelet counters. These dogs do not require treatment for thrombocytopenia.

The high prevalence of macrothrombocytopenia (large platelets plus thrombocytopenia) in the Cavalier King Charles Spaniel (CKCS) is well-recognized. Platelets counts are moderately low (30-90, 000/µL), but these dogs rarely have signs of bleeding. Platelets in this breed should be counted manually, because automated blood cell counters cannot distinguish the large platelets from erythrocytes and therefore underestimate the true platelet count. Thus, members of this breed often exhibit idiopathic asymptomatic thrombocytopenia.

In the study of Peterson and colleagues (2002), platelet counts were studied in 105 clinically healthy CKCS from Scandinavia; 81 offspring and 26 parents. Age, gender, or heart murmur (mitral insufficiency being common in this breed) did not influence the measured manual platelet counts. Thrombocytopenia was found in 46% of the parents, but the mean parental platelet count had no influence on the platelet counts of the offspring. Pedigree analysis indicated that the thrombocytopenia segregated as an autosomal recessive trait, and that 100,000 platelets/µL was the expected lower limit of normal.

References: Dodds, J, Lab Clin Med. 82: 560-565, 1973; Knowler, et al, J Am Vet Med Assoc. 205: 1557-1561, 1994; Dodds, J, Clin Biochem Dom Anim, 5th ed. 1997, pp 241-283; Pedersen et al, J Vet Int Med 16: 169-173, 2002.