Giant platelet disorder in the Cavalier King Charles Spaniel
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Sara M Cowan1, Joseph W Bartges, Rebecca E Gompf
1University of Tennessee College of Veterinary Medicine, Knoxville, TN 37901, USA. saramcowan@yahoo.com
Insights
A benign inherited giant platelet disorder affects about half of Cavalier King Charles Spaniels, causing low platelet counts or larger platelets. This condition impacts platelet aggregation but has normal platelet structure.
Area of Science:
- Veterinary Hematology
- Canine Genetics
- Platelet Physiology
Background:
- Cavalier King Charles Spaniels (Cavaliers) are predisposed to various health conditions.
- Platelet disorders can have significant clinical implications in dogs.
- Understanding platelet characteristics in Cavaliers is crucial for their health management.
Purpose of the Study:
- To characterize the clinical, functional, and morphologic features of platelets in Cavalier King Charles Spaniels.
- To identify potential associations between platelet abnormalities and other clinical findings in the breed.
Main Methods:
- Collected blood samples from 69 clinically normal Cavaliers.
- Performed automated and manual platelet counts.
- Assessed platelet aggregation in response to adenosine diphosphate (ADP).
- Examined platelet ultrastructure using electron microscopy.
Main Results:
- Thrombocytopenia (low platelet count) was observed in 51.43% of Cavaliers.
- Macrothrombocytes (large platelets) were present in 33.33% of dogs.
- Mean platelet aggregation in response to ADP was significantly lower in Cavaliers compared to controls (38% vs 79%).
- Platelet electron microscopy revealed normal and giant platelets with normal internal morphology.
Conclusions:
- Cavalier King Charles Spaniels exhibit a benign inherited giant platelet disorder.
- This disorder is characterized by thrombocytopenia, macrothrombocytes, and reduced ADP-induced platelet aggregation.
- Platelet ultrastructure is normal, and standard anticoagulants (citrate or EDTA) yield accurate counts.
- Cavaliers may serve as a valuable model for studying inherited giant platelet disorders.
Objective:
The aim of this study was to describe the clinical, functional, and morphologic characteristics of platelets in Cavalier King Charles Spaniel dogs (Cavaliers).
Materials And Methods:
Blood from 69 clinically normal Cavaliers was collected and anticoagulated with ethylenediamine-tetraacetic acid (EDTA) and citrate. Automated and manual platelet counts were obtained. Percent platelet aggregation in response to ADP (2, 4, 8, 16, and 32 microM) was determined. Electron microscopy was performed to examine platelet internal morphology and dense granule distribution. A cardiologist recorded the quality of murmurs.
Results:
Thrombocytopenia (<100,000/microL) was present in 51.43% (36/69) of Cavaliers. Macrothrombocytes (>3 microm) were present in 33.33% (22/69). Mean manual platelet count was 118,770/microL. Manual (EDTA blood) and automated (EDTA and citrated blood) methods of platelet counting were correlated. Prevalence of cardiac murmurs was 38% (26/69). There was no association between affected dogs and murmur, signalment, or coat color. Mean percent platelet aggregation was significantly higher in controls than in Cavaliers (79% vs 38%, p=0.001). Response to ADP was unaffected by thrombocytopenia, macrothrombocytes, murmur, or any combination thereof. Platelet electron microscopy showed normal and giant sized platelets with normal internal morphology.
Conclusions:
A benign inherited giant platelet disorder affects approximately 50% of Cavalier King Charles Spaniels. It is characterized by thrombocytopenia, macrothrombocytes, or decreased platelet aggregation in response to ADP. Platelet ultrastructure is normal. Citrated or EDTA blood provides accurate platelet counts. Further studies are indicated to determine platelet glycoprotein structure and any association with mitral endocardiosis. Cavaliers may be useful models of inherited giant platelet disorders.
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