κ Light-chain monoclonal gammopathy and cast nephropathy in a horse with multiple myeloma.

The research focuses on a case study of a 27-year-old Dutch Warmblood mare diagnosed with multiple myeloma, a rare condition in horses. Monoclonal gammopathy and cast nephropathy manifested as key symptoms of the disease.

Clinical Description and Findings

The horse showed several symptoms including:

• Lethargy or fatigue
• Reluctance to move
• Weight loss
• Persistent hyperproteinemia (elevated protein levels in the blood)
• Recurrent bouts of mild lameness

Upon further evaluation, the horse was discovered to have anemia, thrombocytopenia (low platelet count), and hyperproteinemia accompanied by hyperglobulinemia (high globulin levels) and hypoalbuminemia (low albumin levels).

Protein electrophoresis of serum and urine samples revealed a monoclonal gammopathy, a condition characterized by the presence of an abnormal protein, called a paraprotein, in the blood. The paraprotein in this case was identified as a κ light chain.

Further tests, such as abdominal ultrasonographic examinations and splenic fine-needle aspirate cytology, found hypoechoic nodules in the spleen. A bone marrow biopsy sample’s histologic examination confirmed the presence of plasma cell myeloma.

Treatment and Outcome

Given the horse’s old age and the disease’s poor prognosis, the owner declined treatment. After being discharged from the hospital, the horse was given palliative care instructions, but unfortunately, it was euthanized two weeks later due to recurring episodes of lethargy, anorexia, and signs of colic.

Necropsy after euthanization confirmed the diagnosis of multiple myeloma. Moreover, plasma cell aggregates in the liver, spleen, bone marrow, and kidney, along with the presence of cast nephropathy (kidney damage caused by the build-up of free light chains), validated the clinical findings.

Clinical Relevance

Multiple myeloma is a rare condition in horses. This research underscores the importance of considering neoplasia (formation of tumors) in horses exhibiting non-specific clinical signs. The presence of a monoclonal peak on serum protein electrophoresis could indicate neoplasia, specifically multiple myeloma.