SEVERE NONCIRRHOTIC HYPERAMMONEMIA: WHAT UREA- LLY SHOULD CONSIDER S Wu, C Basilio MD, MPH Department of Medicine, Tulane Health Sciences Center, New Orleans, LA
INTRODUCTION Hyperammonemia is often the result of liver pathology. When hyperammonemia is not the result of liver disease, an occult disorder of metabolism must be on the differential for unexplained hyperammonemia, such as a urea cycle disorder.
CASE A 57-year-old man with recovered systolic heart failure, atrial fibrillation, hypertension, and cervical neck fracture status post recent cervical spine corpectomy and fusion presented with worsening dysphagia and neck discomfort and was found to have a cervical fluid collection. He had no known underlying liver disease and denied significant alcohol history. He received a dexamethasone taper and a lumbar drain. He was later admitted to the intensive care unit (ICU) for unstable atrial fibrillation with rapid ventricular rates. In the ICU, the patient became more somnolent and was unable to follow commands. Encephalopathy workup revealed elevated BUN with normal creatinine, ammonia of 772, and mildly elevated transaminases. Liver workup was normal. Workup for inborn errors of metabolism showed mildly decreased citrulline. Urine and plasma amino acids were otherwise normal. His hyperammonemia resolved and his mentation improved with lactulose three times daily and rifaximin twice daily. Urea cycle disorder gene panel and further genetic workup is ongoing. Patient will follow up with genetics after discharge. DISCUSSION Patients with elevations of ammonia present with encephalopathy, which may progress quickly to cerebral herniation. Survival requires immediate reduction of ammonia levels. Although the differential for hyperammonemia is broad, inborn errors of metabolism (IEM), like a urea cycle disorder, should be considered when hyperammonemia is of unclear etiology. Although IEMs often have early age of onset, urea cycle disorders have multiple modes of inheritance and can present at later stages. IEMs may also be unmasked by steroid therapy, which is plausible in this patient who was on a steroid taper prior to his hyperammonemic state. Treatment for a potential IEM begins prior to confirmation of an etiology. Geneticists should be consulted early on for evaluation and management.
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