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Multiple Myeloma

Lobo, an approximately 7-year-old neutered male Chihuahua, presented for evaluation of vomiting and bloody diarrhea.  The owners had just obtained the patient the previous day from a rescue organization, so the age was approximate, not exact.  Additionally, the owners did not know much of the previous medical history other than he has never really walked correctly with his hind limbs.

Initial physical examination revealed most of the teeth to be missing, mild dehydration, and a possible heart murmur present (graded as III/VI with PMI on the left apex).  His posture was abnormal with his rear limbs being held in flexion at the stifle(the weight-bearing surface), and with hyperflexion of the hock and the tarsus held in varus position.  When he ambulated, he would walk mainly on his forelimbs.  However, when he rested, he would balance on the condyles of the femurs.

Lab work revealed a stress leukogram, mild hypoglycemia, decreased creatinine, hypoalbuminemia, and mild elevations in the liver enzymes.  Screening for pancreatitis was normal at this time (SNAP cPL).  Radiographs of the chest and abdomen revealed (upon initial, cursory examination) mild to moderate dilation of the esophagus and an abnormal appearance to the bones of the ischium, ilium, femurs, and tibias.  The abnormal appearance was initially thought to be due to changes from lack of use (as he was reported to not use his legs for many years).  Abdominal ultrasound revealed a mildly nodular pattern to the liver, thickening of the gall bladder wall, and an enlarged mesenteric lymph node as the most significant findings.Aspirates of the mesenteric lymph node revealed abnormal numbers of lymphoblasts, but more importantly, a significant increase in the number of plasma cells.This was initially interpreted as marked reactive hyperplasia by the clinical pathology laboratory.  However, when considered in conjunction with the skeletal changes, another diagnosis was possible.  

After more careful investigation of the radiographs, it was determined that there was a mottled lytic appearance to the ilium, ischium, femur, tibia, humerus, and ulna bilaterally, along with the same changes noted in the thoracic, lumbar, sacral, and caudate vertebrae.  These findings combined were most consistent with multiple myeloma; however, biopsy (of the marrow and the bone) would be required for definitive diagnosis.

Lobo was initially hospitalized with IV fluids and IV antibiotics, along with dextrose supplementation.  After the owners were made aware of the likely diagnosis, they decided to relinquish Lobo to a rescue organization (Furry Friends Refuge).  Thankfully, the rescue organization elected to pursue treatment, and Lobo received an infusion of pamidronate as well as initiating chemotherapy.  At last report, Lobo was doing well and enjoying life!

Plasma cell tumors can present as a single entity (such as a solitary osseous or extramedullaryplasmacytoma) or as a diffuse disease (such as multiple myeloma).  Multiple myeloma, as suspected here, usually results in a hyperglobulinemia (which will often be a monoclonal gammopathy if evaluated with protein electrophoresis), an increase in plasma cells in the bone marrow, anemia (often), hypoalbuminemia (often), and lytic lesions in the bone about half of the time.  Occasionally, these patients will have such high globulins that they will get hyperviscosity syndrome, which can also result in hypertension and retinal hemorrhages.  Treatment for this disease usually involves an alkylating agent and steroids.  In this case, because of the extent of the lysis of the bone, a bisphosphonate was also utilized.  Prognosis is usually good for reduction in clinical signs, but rarely is a cure achieved.

Published on October 4, 2016

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