Urea Cycle Disorders - Causes, Symptoms, Diagnosis And Treatment


Urea cycle disorders (UCDs) are a rare group of diseases, which cause difficulty in removing waste from the body after digestion. UCDs affect the removal of waste that is made from breaking down protein. Protein is essential for the proper functioning of your body, which can be obtained through the consumption of dairy products, meat, fish etc. The consumed protein is then required to be broken down into amino acids, so as to be utilised by your body .

UCDs are inherited diseases and occurs in both children and adults. It can be passed down from the parent to the child. The disorders are included in the category of inborn errors of metabolism. That is, the disorders develop as a result of genetic mutations that cause defects in the nitrogen (extra) metabolism .

UCDs are extremely rare. It happens to one in 30,000 newborns. The onset of the disorders can be neonatal onset or late onset. About 69% of the disorder develop after the newborn period (neonatal onset) .

In the case of newborns, the disorder will result in them being fatally ill within the first 36-48 hours of birth. Whereas for adults, the disorder can go unnoticed for a long period of time. Because, in comparison to infants, adults tend to develop it in mild form and can still produce urea cycle enzymes that will aid in removing the ammonia. This will go on until an internal complication interferes with the function of the enzyme .

The UCDs are of eight different types. The disorders are named in accordance with the missing component in the urea cycle .

The genetic disorders are passed down from the parent to the child. In order for an infant to develop the condition, they must receive a defective gene from both the parents. However, there is an exception in the case of OTC, as it is passed down from the mother to the child (mostly male).

If both the parents have the defective gene, there is  

In the case of OTC deficiency, the development of the disorder is dependent on the fact that whether the child is male or female. If the mother is the carrier of the defective gene, there is  

The signs of the disorder vary according to the age of onset and the type of the disorder. In accordance with the symptoms, UCDs fall into two categories: complete UCD and partial UCD.

When the infant or the adult has partial UCD (the affected will be able to make some of the enzymes), the symptoms will be

The symptoms of partial UCD may not be noticed for months, or in some cases even years.

In the case of complete UCD, which is the complete lack of an enzyme, the symptoms will be noticeable. It usually develops in infants and will arise within the first couple of days. The symptoms will be

The doctor will examine the development of UCDs by carrying out urine tests and blood tests. These tests will aid the doctor in analysing the high ammonia levels and the abnormal metabolites (a substance that is produced by metabolism) .

The doctor will carry out a liver biopsy so as to analyse the levels of enzyme activity.

Genetic tests will be carried out to understand the possibility of problems with the genes that are required to break down the proteins in the urea cycle. This will help in identifying and understanding the exact type of UCD .

An MRI or a CT scan will be carried out to examine whether there are any swellings in the brain; caused by the presence of ammonia in the blood.

The disorder requires lifelong treatment, which will not essentially cure the condition. However, it will help in managing the symptoms     .

In some cases, medications will be required to remove the extra nitrogen and ammonia from the body.

The individual will be required to undergo diets that avoid protein-rich foods. They can consume calorie-rich foods such as fruits, vegetables and starches. With time, the dietician will help in incorporating protein into your daily diet, as it is inevitable for growth.

These will be required depending upon the type of the UCD the individual has. Amino acid supplements such as arginine or citrulline may be added to the diet, so as to aid your body in developing proteins required for tissue repair and growth.

As the production of urea cycle enzymes is carried out in the liver, a liver transplant will help in treating the disorder.

Some of the other ways are by drinking plenty of water, consuming supplements of fat and sugar and dialysis to remove ammonia from the blood.

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