CASE REPORTS/CLINICAL VIGNETTES Hyperammonemic Coma—Barking Up the Wrong Tree

Hepatic encephalopathy and myxedema coma share clinical features: coma, ascites, anemia, impaired liver functions, and a “metabolic ” electroencephalogram (EEG). Hyperammonemia, a hallmark of hepatic en-cephalopathy, has also been described in hypothy-roidism. Differentiation between the 2 conditions, recognition of their possible coexistence, and the conse-quent therapeutic implications are of utmost impor-tance. We describe a case of an 82-year-old woman with a history ofmild chronic liver disease who presentedwith hyperammonemic coma unresponsive to conventional therapy. Further investigation disclosed severe hypothy-roidism. Thyroid hormone replacement resulted in gain of consciousness and normalization of hyperammone-mia. In patients with an elevated ammonia level, altered mental status, and liver disease, who do not have a clear inciting event for liver disease decompensation, over-whelming evidence of hepatic decompensation, or who do not respond to appropriate therapy for hepatic encephalopathy, hypothyroidism should be considered and evaluated. KEY WORDS: hepatic encephalopathy; myxedema coma; urea cycle; hyperammonemia; autoimmune polyglandular syndrome type 2; autoimmune hepatitis