Ornithine transcarbamylase deficiency (OTCD) is a disorder of urea cycle metabolism and ammonia detoxification characterized by either a severe, neonatal-onset disease found almost exclusively in males, or later-onset (partial) forms of the disease. Both present with episodes of hyperammonemia that can be fatal and which can lead to neurological complications. The disease is ornithine carbamoyltransferase deficiency (Monarch Disease Ontology term MONDO_0010703). Also known as: OCT deficiency, OTC deficiency, OTCD, deficiency of citrulline phosphorylase, ornithine carbamoyltransferase deficiency disease, ornithine transcarbamylase deficiency.