HYPERAMMONEMIC COMA IN A PATIENT WITH ORNITHINE TRANSCARBAMYLASE DEFICIENCY

Abstract

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Ornithine transcarbamylase (OTC) deficiency is a rare, X-linked inherited disorder of the urea cycle affecting 1 in 80,000 live births. It is characterized by the inability to break down nitrogen to urea. The resulting hyperammonemia leads to lethargy, hypotonia, seizures and developmental delay if the illness manifests in infancy, and migraines, ataxia, hyperammonemic coma in adults. Early recognition and treatment of hyperammonemia is the key to prevent neurological disability in infancy and hyperammonemic coma leading to death in adults. CASE PRESENTATION: 46-year-old female with past medical history of partial OTC deficiency and complex partial seizures presented to the hospital with chief complaint of altered mental status. In the emergency department, vitals were remarkable for tachycardia. Exam was significant for altered mental status and a Glasgow Coma Scale of 8. Initial labs were significant for hyperammonemia (234 mcmol/L), hypernatremia (160 mmol/L) and abnormal urinary analysis with signs of infection. Patient was admitted to the intensive care unit followed by initiation of lactulose and rifaximin for treatment of hyperammonemia. She was also started on broad spectrum antibiotics for suspicion of urinary tract infection. Electrolyte abnormalities were gradually corrected. However, her condition kept on deteriorating to the point that she was not responding to verbal, tactile or painful stimuli. She was subsequently intubated on the second day of hospitalization due to failure to protect airway. Serial ammonia levels were monitored that kept on increasing. Electroencephalogram showed severe metabolic encephalopathy without seizures. Computerized tomography scan of the brain did not show acute intracranial process. At this point, nephrology was consulted, and patient underwent continuous renal replacement therapy with dramatic improvement of serum ammonia level and her neurological status. This was followed by successful extubation and a gradual return to baseline mental status. She was continued on lactulose, rifaximin and advised to remain on low protein diet. DISCUSSION: This case highlights the rare complication of hyperammonemic coma in an adult patient with history of OTC deficiency. It is an X-linked defect with variable onset and presentation depending on the sex and activity of the enzyme. Patients classically present with lethargy, seizures and hyperammonemia leading to metabolic encephalopathy, coma and death. Diagnosis involves serum amino acid quantitative analysis and urinary orotic acid concentration in urine. Low serum citrulline and elevated urinary orotic acid levels confirm the OTC deficiency. DNA sequencing-based mutation analysis can also be used as first line for diagnosis. Treatment involves rapidly decreasing serum ammonia with lactulose, rifaximin or dialysis. Prognosis depends on the age of presentation and duration of hyperammonemia. CONCLUSIONS: XXX. REFERENCE #1: Summar, Marshall. "Current strategies for the management of neonatal urea cycle disorders." The Journal of pediatrics 138, no. 1 (2001): S30-S39. DISCLOSURES: No relevant relationships by Fatima Ayub, source=Web Response No relevant relationships by Muhammad Hasib Khalil, source=Web Response