Hyperammonemia: An Unusual Cause of Encephalopathy in Multiple Myeloma.

Multiple myeloma (MM) is a malignancy of plasma cells that commonly presents with kidney dysfunction, hypercalcemia, bone pain, and anemia. Although many patients exhibit these symptoms, other, less obvious presentations can complicate the prognosis. In this case report, we describe a 65-year-old African American female with known IgG Kappa MM, who initially presented with back pain - a common symptom associated with bone involvement in MM. However, during her hospital stay, she developed a profoundly altered mental status, which was later linked to elevated ammonia levels. Hyperammonemia is a rare but highly fatal complication in MM. Thus, all providers must be able to clinically recognize and understand how to potentially treat hyperammonemic encephalopathy in MM early in its course.