Causes and risk factors
Hereditary urea cycle results when liver does not produce enough enzymes to change ammonia [NH3] into urea. There are 6 types of amino acids involved – arginine, argininosuccinate, carbamoyl phosphate synthetase, citrulline, N-acetylglutamate synthase, ornithine transcarbamylase. Some genetic mutations may lead to this disorder. Urea cycle consists of several biochemical reactions in which nitrogen [byproduct of protein metabolism] is removed from blood and converted into a compound called urea. This urea is transferred to urine and removed from body. In this disorder, nitrogen accumulates in blood in the form of ammonia. Increased levels of ammonia in blood, reaching brain can cause severe brain damage, coma, and death.
Clinical presentation
Depending upon 6 types of amino acids, 6 types of diseases are produced namely arginase deficiency [AG], argininosuccinate aciduria [ASL], carbamoyl phosphate synthetase deficiency [CPS1], citrullinemia [ASS1], N-acetylglutamate synthetase deficiency [NAGS], ornithine transcarbamylase deficiency [OTC] – Patient presents with poor feeding, decreased food intake. Disliking protein-containing foods is observed. The patient has increased sleepiness, difficulty waking up. Nausea, vomiting occurs. Confusion occurs.
Investigation
Medical history by the patient and clinical examination by the doctor helps in diagnosis. Urine analysis is done. Blood test is required. Imaging studies such as CT scan, MRI may be useful for further evaluation. Genetic testing is advised.
Treatment
Dietary modifications such as limiting protein rich diet, avoiding fasting is essential which will help in managing the disease. Hospitalization is necessary in some cases. Dialysis may help in removing excess ammonia from blood.
