An Unusual Cause of Altered Mental Status in Multiple Myeloma: An Extraosseous Manifestation.

Multiple myeloma typically presents as lytic bony lesions, hypercalcemia, anemia, and renal failure. Extraosseous manifestations are rare. We report on a patient who was recently diagnosed with multiple myeloma and completed the first cycle of bortezomib, dexamethasone, and palliative radiation therapy with good response. Two weeks after discharge, she became confused and was re-admitted. Despite treatment with lactulose and rifaximin, altered mental status worsened. Computer tomographic scan of abdomen showed hepatomegaly and numerous ill-defined small hyperdense nodules scattered throughout the liver. Liver biopsy demonstrated aggregation of plasma cell myeloma. Magnetic resonance imaging of brain revealed dural thickening. Patient's altered mental status was likely from leptomeningeal myelomatosis and hyperammonemic encephalopathy. Although extraosseous manifestations in multiple myeloma including liver and leptomeningeal involvement are rare, its incidence has increased. This condition portends a poor prognosis. The non-specific manifestations of extraosseous myeloma can be confused with complications of multiple sclerosis and lead to incorrect management, thus clinicians should be aware of these pathologies and perform proper diagnostic tests including imaging and tissue pathology. The most effective treatment is unknown, however bortezomib and thalidomide show promise.