Unusual late-onset OTC deficiency pedigree demonstrating male-to-female transmission.466 Patient VI-a had multiple episodes of hyperammonemia starting at 9 years of age; his hepatic OTC activity was 7 percent of normal. He died in hyperammonemic coma at 19 years of age. Patients VI-b and VI-c have had episodes of hyperammonemia (starting in childhood) associated with orotic aciduria. Patient VI-d died from liver failure at 9 months of age; he had normal hepatic OTC activity. Patient V-a had a positive allopurinol test result. Patient IV-a died of “encephalitis.” Patient IV-b died during his first episode of hyperammonemic coma at 44 years of age. Patient IV-c is mentally retarded. Patient IV-d had an episode of hyperammonemic encephalopathy diagnosed as Reye's syndrome at 30 years of age.464 Patient IV-e had multiple episodes of hyperammonemia and had hepatic OTC activity that was 26 percent of normal.313 Both patients IV-d and IV-e had positive allopurinol test results. There is no known consanguinity, nor are the female spouses in the pedigree related. Source: Urea Cycle Enzymes, The Online Metabolic and Molecular Bases of Inherited Disease Citation: Valle D, Beaudet AL, Vogelstein B, Kinzler KW, Antonarakis SE, Ballabio A, Gibson K, Mitchell G. The Online Metabolic and Molecular Bases of Inherited Disease; 2014 Available at: https://ommbid.mhmedical.com/DownloadImage.aspx?image=/data/books/971/ch85fg20.png&sec=62675149&BookID=971&ChapterSecID=62674945&imagename= Accessed: September 27, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved