title: Ornithine transcarbamylase deficiency combined with type 1 diabetes mellitus - a challenge in clinical and dietary management.
abstract: Ornithine transcarbamylase (OTC) deficiency is the most common urea cycle defect. The clinical presentation in female manifesting carriers varies both in onset and severity. We report on a female with insulin dependent diabetes mellitus and recurrent episodes of hyperammonemia. Since OTC activity measured in a liver biopsy sample was within normal limits, OTC deficiency was initially excluded from the differential diagnoses of hyperammonemia. Due to moderately elevated homocitrulline excretion, hyperornithinemia-hyperammonemia-homocitrullinuria-syndrome was suggested, but further assays in fibroblasts showed normal ornithine utilization. Later, when mutation analysis of the OTC gene became available, a known pathogenic missense mutation (c.533C>T) in exon 5 leading to an exchange of threonine-178 by methionine (p.Thr178Met) was detected. Skewed X-inactivation was demonstrated in leukocyte DNA. In the further clinical course the girl developed marked obesity. By initiating physical activities twice a week, therapeutic control of both diabetes and OTC deficiency improved, but obesity persisted. In conclusion, our case confirms that normal hepatic OTC enzyme activity measured in a single liver biopsy sample does not exclude a clinical relevant mosaic of OTC deficiency because of skewed X-inactivation. Mutation analysis of the OTC gene in whole blood may be a simple way to establish the diagnosis of OTC deficiency. The joint occurrence of OTC deficiency and diabetes in a patient has not been reported before.
authors.affiliation: Center of Pediatrics and Adolescent Medicine, University Hospital Freiburg, Freiburg, Germany. sarah.gruenert@uniklinik-freiburg.de.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Grünert
authors.forename: Pablo
authors.initials: P
authors.lastname: Villavicencio-Lorini
authors.forename: Bendicht
authors.initials: B
authors.lastname: Wermuth
authors.forename: Willy
authors.initials: W
authors.lastname: Lehnert
authors.forename: Jörn Oliver
authors.initials: JO
authors.lastname: Sass
authors.forename: K Otfried
authors.initials: KO
authors.lastname: Schwab