UCD.- Ornithine Transcarbamylase (OTC) deficiency
Incidence
Is the most common UCD. However never seen in Saudi Arabia. It is a sex-linked disorder. The enzyme defect can be partial (10-20% of cases of hemizygous males). Affects mildly heteroz. females.
Clinical Characteristics
Severe lethargy, hypotonia, vomiting, seizures in the neonatal period, often fatal. In less severe cases, FTT, headache & vomiting followed by lethargy & stupor following protein ingestion. Severe hyperammonemia. Behavior abnormalities in heteroz. females Neonates are normal during the first 24-48 hours. Then develop the symptoms. Intermittent ataxia seen in heterozigous children.
Precipitants
Protein intake
Provocation Tests
Protein tolerance test. Allopurinol test: following its administration, there is orotidine excreted in the urine.
Diagnostic Procedures
EB liver and small intestine. DB