Background: Hyperammonemic encephalopathy is a rare cause of altered level of consciousness in patients. When investigating encephalopathy, common causes are ischaemic, metabolic, toxic, inflammation, demyelinating, degenerative, hereditary and infection. In this case reports, we present a rare case of encephalopathy in a patient with hyperammonaemia on a background of multiple myeloma. Case presentation: A 67-year old caucasian male with a background history of monoclonal gammopathy of

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... ined significance, presented with confusion, asterixis and recurrent falls. As part of the work up he was found to have a high ammonia level at 123umol/L (normal 0-50umol/L). The patient also had a bone biopsy as he had mild pancytopenia and hyperproteinemia and was diagnosed with multiple myeloma, likely a progression from his paraproteinemia disorder. The patient significantly improved to his baseline with normalisation of ammonia level once he was commenced with Velcade based chemotherapy as well an adjunctive treatment with lactulose. Conclusion: Hyperammonemia in multiple myeloma is a rare but an important differential in patients with encephalopathy. The diagnosis of this is important so that an appropriate treatment can be provided.