What is the Difference Between Type I and Type 2 Citrullinemia?
🆚 Go to Comparative Table 🆚Type 1 and Type 2 Citrullinemia are two different inherited disorders that affect the urea cycle, a sequence of chemical reactions that take place in liver cells. Both conditions are caused by genetic mutations, but they have distinct characteristics, symptoms, and treatments.
Type 1 Citrullinemia:
- Caused by a deficiency in the enzyme argininosuccinate synthetase.
- Results in excess nitrogen, in the form of ammonia, and other toxic substances building up in the blood.
- Can be life-threatening in many cases.
- Less commonly, a milder form can develop later in childhood or adulthood, associated with intense headaches, blind spots, and problems with balance and muscle.
Type 2 Citrullinemia:
- Caused by the absence of a mitochondrial aspartate/glutamate carrier protein.
- Chiefly affects the nervous system, causing confusion, restlessness, memory loss, abnormal behaviors, seizures, and coma.
- Most common in the Japanese population, but has also been reported in other populations, including East Asia, the Middle East, the United States, and the United Kingdom.
- Presents in newborns with neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) and, in older children, with failure to thrive and dyslipidemia (FTTDCD).
In summary, Type 1 Citrullinemia is characterized by a deficiency in the enzyme argininosuccinate synthetase, resulting in excess nitrogen and toxic substances in the blood, while Type 2 Citrullinemia is caused by the absence of a mitochondrial aspartate/glutamate carrier protein and primarily affects the nervous system. Both conditions are inherited as autosomal recessive traits.
Comparative Table: Type I vs Type 2 Citrullinemia
Here is a table summarizing the differences between Type I and Type II Citrullinemia:
| Feature | Type I Citrullinemia (CTLN1) | Type II Citrullinemia (CTLN2) |
|---|---|---|
| Cause | Mutation in the ASS gene | Mutation in the SLC25A13 gene |
| Frequency | Rare, with a frequency of about 1:100,000 in Japan | Rare, with varying frequencies depending on ethnicity |
| Symptoms | Hyperammonemia, neurologic sequelae, and intellectual disability | Recurring episodes of hyperammonemia, neurologic and psychotic symptoms |
| Age of Onset | Varies, with both neonatal acute and milder late-onset forms | Presents in newborns with neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) and later in older children as failure to thrive and dyslipidemia |
| Treatment | No known method for prevention, but prenatal diagnosis is available | Diagnosis involves laboratory testing, including measurement of ammonia levels and enzyme activity |
Please note that the information in this table is based on the provided search results and may not be exhaustive.
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