Multiple myeloma-induced hyperammonemic encephalopathy: an entity associated with high in-patient mortality.

Hyperammonemia attributed to multiple myeloma (MM) has been rarely reported. We present 6 patients from our institution and 34 from the literature with MM-induced hyperammonemic encephalopathy. The median age was 67 years with male:female ratio of 1.8:1. The median ammonia level was 114 umol/L. IgG and IgA MM was seen in 40% and 35% of cases, respectively. The in-patient mortality was 48%. The in-patient mortality was 31% in patients who received MM-directed therapy and 100% in those who did not received MM-directed therapy. Hyperammonemic encephalopathy is a rare complication in MM and is associated with high in-patient mortality.