Benefits of tailored disease management in improving tremor, white matter hyperintensities, and liver enzymes in a child with heterozygous X-linked ornithine transcarbamylase deficiency

Ashley Andrews; Sarah Roberts; Lorenzo D Botto

doi:10.1016/j.ymgmr.2022.100891

Benefits of tailored disease management in improving tremor, white matter hyperintensities, and liver enzymes in a child with heterozygous X-linked ornithine transcarbamylase deficiency

Mol Genet Metab Rep. 2022 Jul 2;33(Suppl 1):100891. doi: 10.1016/j.ymgmr.2022.100891. eCollection 2022 Dec.

Authors

Ashley Andrews¹, Sarah Roberts¹, Lorenzo D Botto¹

Affiliation

¹ Department of Pediatrics, Division of Medical Genetics, University of Utah, Salt Lake City, UT, USA.

Abstract

We report the case of a 19-month-old girl with late-onset ornithine transcarbamylase (OTC) deficiency initially referred to gastroenterology for intermittent vomiting lasting a year and abnormal liver enzymes (AST 730 U/L [reference range 26-55 U/L]; ALT 1213 U/L [reference range 11-30 U/L]) without hepatomegaly. While the patient was hospitalized for liver biopsy, intermittent tremors of the upper extremities with varying severity were noted. The patient was presumed to have hyperammonemia secondary to acute liver failure and was discharged after 5 days; follow-up monitoring led to readmission 7 days later. A brain MRI showed nonspecific bilateral pericallosal and bifrontal white matter FLAIR hyperintensities. These findings raised suspicion for a metabolic disease and prompted a genetics consultation. After inconclusive biochemical testing and worsening clinical status, rapid whole genome sequencing results were obtained identifying a novel, de novo, likely pathogenic, variant c.608C > T (p.Ser203Phe) in the OTC gene. The patient was promptly started on an oral nitrogen scavenger, citrulline supplementation, and protein restriction. Ammonia and glutamine levels normalized within 1 month of treatment and have stayed within the goal ranges with continued tailoring of treatment. Her parents noted resolution of vomiting and improved mood stability. Liver enzymes normalized after 2 months of treatment. The tremor, identified as asterixis, improved and a repeat brain MRI 3 months after the initial imaging showed near-complete resolution of previous white matter hyperintensities.

Keywords: ALT, alanine transaminase; AST, aspartate aminotransferase; Asterixis; BASC-3, Behavior Assessment System for Children; BCAA, branched-chain amino acid; FLAIR, fluid-attenuated inversion recovery; GGT, gamma-glutamyl transferase; Late onset; MRI, magnetic resonance imaging; MRS, magnetic resonance spectroscopy; Manifesting heterozygote; OTC, ornithine transcarbamylase; Ornithine transcarbamylase deficiency; PT, prothrombin time; Partial onset; TID, 3 times a day; UCD, urea cycle disorder; Urea cycle disorder; WPPSI-IV, Wechsler Preschool and Primary Scale of Intelligence; X linked.