Brief H&P

A 38 year-old male with unknown medical history is brought to the emergency department by EMS with agitation and bizarre behavior. According to prehospital report, the patient was acting erratically – shouting incomprehensibly in the middle of a busy street with possible associated seizure activity.

On evaluation, the patient was found to be tachycardic, hypertensive, and markedly agitated. Physical examination with a focus on toxidromes was notable for the presence of rotary nystagmus suggestive of hallucinogen including phencyclidine toxicity. The patient required pharmacologic sedation to allow for a broad evaluation of altered mental status.

ED Course

The patient’s workup including core temperature, head imaging and laboratory tests (including AST/ALT, albumin, INR) were unremarkable with the exception of an ammonia level of 142 umol/L (normal range 16-53), slightly elevated CK, and urine toxicology screen with multiple positive agents. Over the course of several hours in the emergency department, the patient’s mental status gradually improved reaching normal level of alertness and orientation with normal neurological examination. He acknowledged PCP use as well as a prior history of seizures (possibly related to ethanol withdrawal) without routine anti-epileptic drug use. He denied known history of liver disease.

The patient’s hyperammonemia was attributed to a hypercatabolic state secondary to phencyclidine-induced agitation with possible seizure. He was discharged with resources for assistance with substance cessation.

An Algorithm for the Differential Diagnosis of Hyperammonemia:

Algorithm for the Differential Diagnosis of Hyperammonemia


  1. Kalra A, Norvell JP. Cause for Confusion: Noncirrhotic Hyperammonemic Encephalopathy. Clin Liver Dis. 2020;15(6):223-227. doi:10.1002/cld.929
  2. Mallet M, Weiss N, Thabut D, Rudler M. Why and when to measure ammonemia in cirrhosis? Clin Res Hepatol Gas. 2018;42(6):505-511. doi:10.1016/j.clinre.2018.01.004
  3. Hassan AAI, Ibrahim W, Subahi A, Mohamed A. ‘All that glitters is not gold’: when hyperammonaemia is not from hepatic aetiology. Bmj Case Reports. 2017;2017:bcr-2017-219441. doi:10.1136/bcr-2017-219441
  4. Odigwe CC, Khatiwada B, Holbrook C, et al. Noncirrhotic Hyperammonemia Causing Relapsing Altered Mental Status. Bayl Univ Medical Cent Proc. 2017;28(4):472-474. doi:10.1080/08998280.2015.11929312
  5. Upadhyay R, Bleck TP, Busl KM. Hyperammonemia: What Urea-lly Need to Know: Case Report of Severe Noncirrhotic Hyperammonemic Encephalopathy and Review of the Literature. Case Reports Medicine. 2016;2016:1-10. doi:10.1155/2016/8512721
  6. Walker V. Severe hyperammonaemia in adults not explained by liver disease. Ann Clin Biochem. 2011;49(3):214-228. doi:10.1258/acb.2011.011206
  7. Laish I, Ari ZB. Noncirrhotic hyperammonaemic encephalopathy. Liver Int. 2011;31(9):1259-1270. doi:10.1111/j.1478-3231.2011.02550.x
  8. LaBuzetta JN, Yao JZ, Bourque DL, Zivin J. Adult Nonhepatic Hyperammonemia: A Case Report and Differential Diagnosis. Am J Medicine. 2010;123(10):885-891. doi:10.1016/j.amjmed.2010.02.029
  9. Clay AS, Hainline BE. Hyperammonemia in the ICU. Chest. 2007;132(4):1368-1378. doi:10.1378/chest.06-2940
  10. Weng T-I, Shih FF-Y, Chen W-J. Unusual causes of hyperammonemia in the ED. Am J Emerg Medicine. 2004;22(2):105-107. doi:10.1016/j.ajem.2003.12.011
  11. Hawkes ND, Thomas GAO, Jurewicz A, et al. Non-hepatic hyperammonaemia: an important, potentially reversible cause of encephalopathy. Postgrad Med J. 2001;77(913):717. doi:10.1136/pmj.77.913.717