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Abstract: SA-PO596

Hyperammonemia in Multiple Myeloma (MM): Rare but Serious Complication

Session Information

Category: Dialysis

  • 801 Dialysis: Hemodialysis and Frequent Dialysis


  • Mai, Erik, Medical University of South Carolina, Charleston, South Carolina, United States
  • Vilayet, Salem, Medical University of South Carolina, Charleston, South Carolina, United States
  • Krishnasami, Zipporah, Medical University of South Carolina, Charleston, South Carolina, United States

MM is characterized by abnormal plasma cell proliferation and clinical manifestations such as hypercalcemia, renal insufficiency, anemia, and bone lesions. Encephalopathy associated with MM can stem from hypercalcemia, hyperviscosity, or uremia. In rare cases, certain myeloma cell lines can cause hyperammonemia which can result in cerebral edema, high intracranial pressure, and high mortality rates. We present a case of hyperammonemic encephalopathy complicating relapsed refractory MM (RRMM) following an autologous stem cell transplant.

Case Description

A 62-year-old African American woman with RRMM following an autologous stem cell transplant presented with bone pain, increasing lethargy and confusion. Laboratory studies showed anemia, thrombocytopenia, low Kappa-Lambda ratio and normal calcium levels. Despite a normal liver function test, she had elevated ammonia levels, peaking at 157.3 umol/L. Her blood gas indicated chronic primary respiratory alkalosis (pH 7.51, PCO2 23mmHg, HCO3- 18mmol/L) due to ammonia- stimulated ventilation. A head CT was negative for acute pathology. Findings were consistent with MM-induced hyperammonemic encephalopathy. Lactulose and rifaximin were started, but her ammonia level remained elevated. To aid in ammonia clearance, she underwent continuous renal replacement therapy (CRRT) at a a dose higher than standard (~35mL/kg/hr), while receiving aggressive chemotherapy (DCEP). After four days, there was an improvement in her ammonia level and mentation, and CRRT was discontinued. However, the patient was readmitted for hyperammonemic encephalopathy and ultimately transitioned to hospice care due to treatment failure.


Hyperammonemic encephalopathy should be considered in MM patients with decreased consciousness. The exact mechanism is unclear but may be related to the production of ammonia by myeloma cell lines or to myeloma-related humoral factors which can affect amino acid metabolism leading to hyperammonemia. While rare, this manifestation may indicate an advanced disease state and an unfavorable prognosis. Management lacks consensus, but chemotherapy is crucial. Lactulose and rifaximin may reduce ammonia levels; however, renal replacement therapy is more effective in ammonia clearance and may prevent complications from prolonged hyperammonemia, including cerebral edema.