Hyperammonemic encephalopathy in multiple myeloma

History and clinical findings: A 54-year old man had suffered from advanced multiple myeloma for two years. After initially good response the myeloma was refractrory to treatment with dexamethasone, cyclophosphamide, bortezomibe, zoledronate and additionally doxorubicine. The patient then complained of dyspnea without clinical signs of cardiopulmonary disease. Investigations: Arterial blood gas analysis showed hyperventilation with respiratory alkalosis and normal alveolo-arterial gradient as the reason for the dyspnea. With a normal MRI of the brain and lumbal puncture, a neurological disease could be excluded. Serum calcium, creatinine and serum viscosity were normal. Eventually, serum ammonia levels were found to be substantially elevated (144 mu mol/l) and hyperammonemic encephalopathy was diagnosed. Treatment and course: Therapy with bortezomib and high dose dexamethason was repeated, and the patient also received bendamustin. Despite this treatment, he lost consciousness and died after two weeks because of aspiration pneumonia. Conclusion: The existence of respiratory alkalosis and multiple myeloma should prompt a search for hyperammonemia.