A Case of Suspected Urea Cycle Dysfunction in a Patient with Unexplained Hyperammonemia

Urea cycle disorders are inherited deficiencies of the enzymes involved in the cellular excretion of excess ammonia produced during protein metabolism. Hyperammonemia associated with these disorders is usually manifested by decreased level of consciousness, irritability, seizures, vomiting, and poor feeding. Although the majority of recognized patients are children, a delayed presentation is seen in patients with partial enzyme deficiency, including heterozygotes. These patients become symptomatic in later childhood or adulthood. Diagnoses of urea cycle defects (UCD) in the adult population have been reported. Often, the diagnosis only becomes apparent during times of increased metabolic stress, such as with acute or chronic illness. Prompt recognition and treatment are essential in determining the outcome of these patients. We present a case of hyperammonemic encephalopathy from a presumed urea cycle defect.