biostudies-literatureUnknown33(Suppl 1)Abbott JHorizon TherapeuticsWe report the case of a medically complex African American adult female with ornithine transcarbamylase (OTC) deficiency diagnosed after lifelong protein aversion and new onset of chronic vomiting and abdominal pain with intermittent lethargy and confusion. Symptomatology was crucial to diagnosis as genetic testing did not identify any pathogenic variants in <i>OTC</i>; however, the patient's diagnosis was delayed despite her having longstanding symptoms of a urea cycle disorder (UCD). Her symptoms improved after treatment with a modified protein-restricted diet, long-term nitrogen-scavenger therapy, and supplemental L-citrulline. Adherence to her UCD management regimen remained a challenge due to her underlying frailty and other medical conditions, which included primary renal impairment Molecular genetics and metabolism reports100916https://www.ebi.ac.uk/biostudies/studies/S-EPMC9817481biostudies-literatureA complex case of delayed diagnosis of ornithine transcarbamylase deficiency in an adult patient with multiple comorbidities.PMC9817481Abbott JSenzatimore MAtwal PfalseA complex case of delayed diagnosis of ornithine transcarbamylase deficiency in an adult patient with multiple comorbidities.We report the case of a medically complex African American adult female with ornithine transcarbamylase (OTC) deficiency diagnosed after lifelong protein aversion and new onset of chronic vomiting and abdominal pain with intermittent lethargy and confusion. Symptomatology was crucial to diagnosis as genetic testing did not identify any pathogenic variants in <i>OTC</i>; however, the patient's diagnosis was delayed despite her having longstanding symptoms of a urea cycle disorder (UCD). Her symptoms improved after treatment with a modified protein-restricted diet, long-term nitrogen-scavenger therapy, and supplemental L-citrulline. Adherence to her UCD management regimen remained a challenge due to her underlying frailty and other medical conditions, which included primary renal impairment 2022-01-01T00:00:00Z2022 Dec2025-04-05T11:24:11.662Z2025-04-05T11:24:11.662ZS-EPMC98174813662038510.1016/j.ymgmr.2022.100916