Simultaneous primary hyperparathyroidism and multiple myeloma in a dog with hypercalcaemia

A 14-year-old male castrated Pomeranian was found to be hypercalcaemic and hyperglobulinaemic during investigation of anorexia and haematochezia. Ionised hypercalcaemia, increased serum parathyroid hormone concentration, normophosphatemia and a parathyroid nodule found on cervical ultrasound examination were diagnostic for primary hyperparathyroidism (PHPT). Thoracic radiographs revealed ovoid lytic lesions in multiple bones. To investigate the hyperglobulinaemia, serum electrophoresis and immunoglobulin (Ig) quantification were performed, revealing an IgA biclonal gammopathy and bone marrow cytopathology confirmed multiple myeloma (MM). Following bilateral parathyroidectomy, the dog's hypercalcaemia resolved, and pulse-dose chemotherapy with prednisone and melphalan was initiated to treat MM. To the author's knowledge, this is a unique case report of simultaneous PHPT and MM in the veterinary literature, diseases that are rarely reported concurrently in humans. This case highlights the need to thoroughly investigate multiple problems when they are not explained by a single diagnosis.