Management of Ornithine Carbamoyltransferase Deficiency with Underlying Hyperammonia Hyperinsulinemia Syndrome

BACKGROUND The urea cycle converts amino acids to urea and is excreted by the kidneys. Ornithine carbamoyltransferase (OTC) deficiency is a rare X-linked urea cycle disorder which results in hyperammonemia. Diagnosis is made based on a clinical presentation of poor feeding, hypotonia, biochemical profile, and genetic testing. Another genetic cause for hyperammonemia is hyperammonia hyperinsulinemia (HAHI) syndrome. A mutation coding for glutamate dehydrogenase (GDH) results in increased alpha-keto glutarate and ATP, triggering the secretion of pancreatic insulin. However, unlike OTC deficiency, these patients are asymptomatic but do have symptoms of hypoglycemia. The purpose of this article is to present the case of a 66-year-old woman with an unusual late-onset of OTC deficiency compounded with an underlying HAHI syndrome with co-disease management. CASE REPORT A 66-year-old female with a history significant for transient ischemic attack (TIA) and urea cycle disorder was admitted for new adverse symptoms. Further evaluation revealed hyperammonemia and hypoglycemia. Despite standard previous treatment for her underlying urea cycle disorder, high ammonia levels and hypoglycemia persisted. The contradicting values with continued hypoglycemia regardless of dextrose treatment was suspicious for underlying HAHI. Further genetic testing during her admission revealed a deletion in GLUD-1 gene concurrent with diagnosis of HAHI. After co-diagnosis was established, effective management required medications for both disorders in concordance with dietary restriction. CONCLUSIONS This is an extremely rare case of OTC deficiency, with a vague presentation in an elderly female. Exploring compounding genetic disorders in the presence of one that is already established and early recognition are crucial for prompt diagnosis and management.