CASE REPORT: INHERITED MACROTHROMBOCYTOPENIA IN A CAVALIER KING CHARLES SPANIEL

A 11-month-old intact male Cavalier King Charles Spaniel (CKCS) dog was presented at the Teaching Hospital of National Chung Hsin University (NCHU-VMTH) due to thrombocytopenia without relevant clinical signs and no significant improvement after medication treatment. As per the complete blood profile, there was significant thrombocytopenia (platelet count 1–[Formula: see text] L) with mean platelet volume (MPV) ranging from 20.3 to 25.7[Formula: see text]fl. Tests for Babesia canis, B. gibsoni, Ehrlichia canis and Anaplasma phagocytophilum yielded negative results. Despite treatment with antibiotics and immunosuppressive drugs, the dog’s condition did not improve. The dog’s platelet morphology and absence of symptoms raised the suspicion of inherited macrothrombocytopenia. Genomic DNA sequencing analysis of the [Formula: see text]1-tubulin gene revealed a single-point mutation, specifically c.745[Formula: see text]G>A. This genetic analysis confirmed the presence of a [Formula: see text]1-tubulin mutation, marking the first reported case of such a mutation in a CKCS in Taiwan. Despite the diagnosis of this condition, both partial thromboplastin time (PTT) and active partial thromboplastin time (aPTT) were within normal ranges before neutering. When diagnosing the causes of thrombocytopenia in young patients, especially when there are no related clinical signs, it is crucial to consider prioritizing inherited macrothrombocytopenia, then thrombocytopenia secondary to parasite infection, or immune-mediated thrombocytopenia (IMT) to minimize unnecessary medication.