Identification and Characterization of Glanzmann Thrombasthenia in 2 Closely Related Mixed‐breed Dogs

A 2-year-old, female intact, mixed-breed dog was presented to the Bailey Small Animal Teaching Hospital at Auburn University for investigation of lifelong, intermittent petechial hemorrhage. Historically, the dog also had excessive gingival bleeding during tooth eruption. The dog was found as a stray and was 1 of a litter of puppies. A male sibling was reported to have a similar history of petechial and ecchymotic hemorrhages and its owner was later contacted and the dog brought to the teaching hospital for platelet aggregation studies. Before referral, the female dog was managed by the referring veterinarian for suspected immune-mediated thrombocytopenia with prednisolone 5 mg PO q12h, doxycycline 5 mg PO q12h, famotidine 10 mg PO q24h, and sucralfate 250 mg PO q8–12h. A SNAP 4DX was negative and other testing, including von Willebrand Factor (VWF) antigen and a coagulation panel was normal (VWF, 113%; reference interval [RI], 70–180%; prothrombin time, 6.6 seconds; RI, 5.5–12; activated partial thromboplastin time, 11.3 seconds; RI, 10–25). The dog consistently had platelet counts just below the lower limit of the RI (170–400 9 10/lL) on referring laboratory tests, but the platelet count was not low enough to account for the platelet-associated bleeding seen. No correlation was identified between increases or decreases in the prednisolone dosage and improvement in platelet counts or the development of petechiation. Immune-mediated vasculitis was suspected before referral to the Bailey Small Animal Teaching Hospital at Auburn University. On presentation, the dog was bright and alert. Routine vaccinations were not current. On physical examination, the dog was moderately overweight and petechiae were noted on the ventral abdomen and the inner left thigh. Laboratory testing identified mild anemia (hematocrit, 38.4%; RI, 38.7–59.2%), a moderate neutrophilia (19,627 lL; RI, 2.6–10.4 9 10/lL), and normal platelet counts (210 9 10/lL; RI, 152– 518 9 10/lL). Serum biochemistry results were normal. Thoracic radiographs were within normal limits, and the hyperechoic appearance of the liver on abdominal ultrasound examination was consistent with the previous history of steroid treatment but otherwise normal. A buccal mucosal bleeding time was markedly abnormal with prolonged mucosal bleeding >5 minutes (RI, ≤5 minutes). Platelet function studies, including platelet aggregation, clot retraction, and flow cytometry were performed. A hereditary platelet function disorder was suspected given the lifelong history of petechial hemorrhage and lack of clinically relevant findings on diagnostic tests performed that could explain an acquired platelet disorder. The owner was contacted to inquire about possible affected littermates, 1 of which was found and tested at a later time. Blood was collected by jugular venipuncture into 3.8% trisodium citrate at a ratio of 9 : 1 from the patient, sibling, and control dogs for isolation of platelet-rich plasma (PRP). Pressure was applied to the venipuncture site for approximately 10 minutes and then wrapped while the patients were hospitalized. Platelet responses to adenosine diphosphate (ADP), collagen, epinephrine, platelet-activating factor (PAF), and gamma thrombin were evaluated in a dual channel platelet aggregometer. ,1 With the exception of epinephrine, platelets from the control dog responded with shape change and irreversible platelet aggregation to all agonists tested. In contrast, platelets from the patient and sibling underwent shape change responses but failed to aggregate in response to all agonists tested From the Bailey Small Animal Teaching Hospital, (Haysom, Smith-Carr); and the Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL (Kennerly, M€ uller, Christopherson, Boudreaux). The study was performed at the Bailey Small Animal Teaching Hospital and the Department of Pathobiology, College of Veterinary Medicine, Auburn, Alabama. The study was not supported by a grant. Corresponding author: L. Haysom, Bailey Small Animal Teaching Hospital, College of Veterinary Medicine, Auburn University, Auburn, AL 36849; e-mail: [email protected]. Submitted September 30, 2015; Revised November 8, 2015; Accepted December 9, 2015. Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. DOI: 10.1111/jvim.13825 Abbreviations: