Hypercalcemia and high serum parathyroid hormone-related protein concentration in a horse with multiple myeloma.

This study examined a case of a 13-year-old horse with symptoms such as weight loss, high protein and calcium levels in the blood, and was later found to have multiple myeloma; a cancer that forms in a type of white blood cell called a plasma cell which impairs the production of normal blood cells and immune system function.

Case Overview

• The horse was brought under examination due to weight loss, increased amounts of protein (hyperglobulinemia), and calcium (hypercalcemia) in the blood.
• Hypercalcemia, an excess of calcium in the blood, could be caused by renal failure, overactivity of the parathyroid glands (primary hyperparathyroidism), vitamin D poisoning, and certain types of cancer (malignancy).
• Based on the absence of vitamin D ingestion history and normal readings of serum creatinine and parathyroid hormone, renal failure and primary hyperparathyroidism were ruled out as causes.
• The excess calcium was initially ascribed to an unidentified malignancy, despite comprehensive testing failing to identify any such neoplastic disease.

Identification of the Disease

• Eight months after the initial examination, elevated levels of parathyroid hormone-related protein (PTHrP) reinforced the hypothesis of malignancy as the cause of the horse’s hypercalcemia.
• A 300-fold increase in serum IgA concentration, identified through radial immunodiffusion tests, was further indication of a health anomaly.
• The patient was ultimately euthanized and a postmortem examination was conducted to identify the illness.

Postmortem Findings and Final Diagnosis

• Cancerous infiltrates were discovered in the kidneys, lymph nodes, liver, and bone marrow.
• The cancerous cells possessed the structural characteristics of plasma cells and the immunohistochemical stains affirmed that these cells were expressing PTHrP and IgA.
• The final diagnosis was multiple myeloma, a cancer of plasma cells that are responsible for producing antibodies. In this case, the abnormal expression of IgA type antibodies (paraprotein) was noted.