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Why are baby boys at high risk for OTC deficiency? The genetic mystery behind it is revealed!
Of all urea cycle disorders, OTC deficiency is the most common and results from mutations in the OTC gene. The gene is located on the X chromosome and therefore affects male babies, putting them at higher risk. As the disease becomes better understood, the medical community begins to uncover the genetic mysteries behind it.
OTC deficiency is caused by a deficiency in the enzyme in the mitochondria responsible for converting carbamate and proline into citrate, a process critical for urea metabolism.
Pathological mechanism of disease
OTC deficiency is mainly due to mutations in the OTC gene that lead to weakened or ineffective activity of the enzyme. The impact is more significant on male infants because they only have one gene on the X chromosome. If this gene is damaged, it will not be able to produce a normally functioning enzyme. The condition is less common in women because they may still have a normal OTC gene on their other X chromosome, although random non-random inactivation of the X chromosome may also cause some women to exhibit severe symptoms.
Clinical manifestations
The clinical manifestations of OTC deficiency vary from individual to individual, especially in male infants. Many patients develop symptoms such as irritability, lethargy and cessation of eating within just a few days after birth. In some cases, if left untreated, patients can rapidly deteriorate and even slip into a coma.
Even patients with mild OTC deficiency may develop severe symptoms when they experience sufficient metabolic stress.
Genetics understanding
OTC deficiency is an X-linked recessive genetic disorder that affects males at a higher rate than females. Because women have two X chromosomes and the normal gene on one of them can still produce part of the OTC enzyme, their symptoms are usually mild and may even be asymptomatic.
In about 10%-15% of mutation cases, gene deletion causes disease. This further adds to the differences in presentation between male and female patients. Therefore, accurate genetic testing is crucial for diagnosis and treatment.
Diagnosis process
In the face of obvious hyperammonemia, doctors first need to quickly reduce the patient's ammonia concentration, and then diagnose the specific cause of OTC deficiency. Diagnosis often involves analysis of blood and urine amino acids and analysis of organic acids in urine to look for characteristic biochemical signs.
Typical biochemical signs include increased ammonia concentration, decreased citric acid and arginine concentrations, and increased squamous acid. This phenomenon is of index significance for the diagnosis of OTC deficiency.
Treatment methods and prospects
The treatment of OTC deficiency focuses on avoiding the occurrence of hyperammonemia. Common treatment options include a low-protein diet and the administration of nitrogen scavengers. If a hyperammonemic event occurs, screening methods such as hemodialysis may be necessary.
The only curative treatment option currently is liver transplantation, which restores normal enzyme activity to patients. According to studies, the five-year survival rate of patients with OTC deficiency who undergo liver transplantation can reach over 90%.
Social influence and cultural response
OTC deficiency has been reflected in various media. For example, in the medical drama series "House, M.D." and "Chicago Med", the disease is used as part of the plot. This not only raises awareness of this rare disease, but also promotes attention to related research.
Today, with the advancement of science and technology, gene sequencing has become an important diagnostic tool for OTC deficiency and other genetic diseases. However, if there is a patient in the family, will future children still face the same risk and how to prevent it?
