A 70‐year‐old woman with progressive stage 3A IgA kappa multiple myeloma presented with a 4‐month history of intermittent delirium and multiple falls. Prior to her hospitalization, she received empiric treatment for a urinary tract infection and pneumonia. Despite treatment, she continued to experience recurrent neurological symptoms resulting in hospital admission. Her medical history was significant for urosepsis, chronic kidney disease and hypertension. She had no history of cirrhosis or new medications. Physical examination revealed a woman who was alert but oriented only to person. She had no stigmata of liver disease. Vital signs were stable. Laboratory values were sodium 146 mmol/L, calcium of 10.9 mg/dL, serum creatinine of 1.2 mg/dL, white blood cell count 4.65 k/μL and hemoglobin 9.0 g/dL Liver function tests were normal. CT and MRI of the head were negative. Electroencephalogram (EEG) was consistent with nonspecific encephalopathy. Due to her history of recurrent urinary tract infections and a positive urinalysis, intravenous ceftriaxone was started. However, her urine and blood cultures remained negative. Pamidronate and calcitonin were given to treat her mild hypercalcemia with normalization of her ionized calcium level. Unfortunately, she became increasingly delirious and acutely decompensated on hospital day 11. Arterial blood gas revealed respiratory alkalosis with a secondary metabolic acidosis (pH, 7.5; carbon dioxide, 21 mmol/L; and bicarbonate, 16.4 mmol/L). CT pulmonary angiography was negative for pulmonary emboli or other process. Repeat cultures were negative. She had no overt evidence for hyperviscosity syndrome. An ammonia level was elevated at 175 μmol/L (normal being less than 47 μmol/L) without evidence of hepatic dysfunction. Despite administration of lactulose, a repeat ammonia level 48 hours later was 185 μmol/L The patient became comatose and subsequently passed away after her family decided to withdraw care.
Common etiologies of altered mental status in patients with multiple myeloma are hypercalcemia, sepsis, drug toxicity and hyperviscosity syndrome. Hyperammonemia in the absence of hepatic dysfunction is a rare finding responsible for altered mental status in patients with progressive multiple myeloma. Although the pathophysiology of hyperammonemia in MM is not clear, in vitro studies have demonstrated myeloma cells in culture producing excess NH4 due to altered amino acid metabolism.
Primary hyperammonemic encephalopathy induced from multiple myeloma needs to be part of the differential of delirium for hospitalists looking after hematological inpatients. The reported mortality rate without primary treatment is greater than 40%. If detected early, encephalopathy can potentially be reversed with chemotherapeutic management of the myeloma.
To cite this abstract:Eaton K, Holmstrom B, Abulhaija A. Hyperammonemic Encephalopathy in Multiple Myeloma. Abstract published at Hospital Medicine 2013, May 16-19, National Harbor, Md. Abstract 505. Journal of Hospital Medicine. 2013; 8 (suppl 2). https://www.shmabstracts.com/abstract/hyperammonemic-encephalopathy-in-multiple-myeloma/. Accessed January 29, 2020.