Immune-mediated thrombocytopenia in a mixed-breed female dog: clinical signs, diagnostic approach, and therapeutic management

Abstract

This case report describes an instance of immune-mediated thrombocytopenia (IMT) in a mixed-breed female dog, systematically detailing all diagnostic steps. The animal presented with cutaneous ecchymoses and hematomas and thrombocytopenia (109,000/µL). Tests were performed to exclude hemoparasitic infections, including a rapid test (4Dx® Plus), serology for canine visceral leishmaniasis, and qualitative PCRs for Leishmania chagasi, Rangelia vitalii, Hepatozoon spp., Ehrlichia spp., Babesia spp., Anaplasma spp., Dirofilaria immitis, and Mycoplasma haemocanis, all of which were non-reactive. Ultrasonographic examination ruled out neoplasia. Prothrombin time (PT) = 10.2 seconds and activated partial thromboplastin time (aPTT) = 29.2 seconds were elevated. Bone marrow evaluation revealed megakaryocytic hyperplasia, indicating a medullary response to platelet destruction. Considering the clinical signs and hematologic alterations (thrombocytopenia, elevated PT and aPTT, megakaryocytic hyperplasia), a presumptive diagnosis of IMT was established, which was confirmed after a favorable response to immunosuppressive therapy with gradually tapered prednisolone, combined with leflunomide as a maintenance treatment. Platelet counts normalized within 15 days, and clinical signs resolved within 20 days. This report highlights the importance of a systematic diagnostic approach and emphasizes leflunomide as a viable option for long-term management of canine IMT.