A 12-year-old mixed breed dog was evaluated for marked hypercalcemia that was identified during assessment for acute polydipsia and polyuria. Physical examination identified a new grade II/VI left apical systolic murmur. A mass involving the left ventricular posterior wall and left atrium was identified by echocardiography, suggesting neoplastic invasion into the myocardium. The patient was euthanized, and post-mortem cardiac evaluation identified an intramyocardial amyloid-producing plasma cell tumor. Multiple myeloma was suspected but could not be confirmed due to the limited post-mortem evaluation. This case is the first report of myocardial amyloidosis in a dog with a myeloma-related disorder (MRD). Dogs with MRD and myocardial involvement may not exhibit clinical signs that localize to the cardiovascular system; therefore, echocardiography should be considered during the staging process.

一只 12 岁的混种狗接受了明显的高钙血症评估，这是在评估急性烦渴和多尿时发现的。体检发现新的 II/VI 级左心尖收缩期杂音。超声心动图发现肿块累及左心室后壁和左心房，提示肿瘤侵犯心肌。该患者被安乐死，尸检心脏评估发现心肌内产生淀粉样蛋白的浆细胞肿瘤。怀疑患有多发性骨髓瘤，但由于尸检评估有限，无法确诊。该病例是首例患有骨髓瘤相关疾病（MRD）的狗出现心肌淀粉样变性的报告。患有 MRD 和心肌受累的狗可能不会表现出仅限于心血管系统的临床症状；因此，在分期过程中应考虑超声心动图检查。