Other hyperphenylalaninemias Save

Understanding Other Hyperphenylalaninemias

Hyperphenylalaninemias are a group of genetic disorders characterized by elevated levels of phenylalanine in the blood. While phenylalanine is an essential amino acid, excessive levels can be harmful to the body. One type of hyperphenylalaninemia is phenylketonuria (PKU), which is well-known and often diagnosed in newborns. However, there are other forms of hyperphenylalaninemias that are less commonly discussed but equally important to understand.

1. Non-PKU Hyperphenylalaninemias: This category includes several subtypes of hyperphenylalaninemias that are not classified as PKU. These disorders are caused by different enzyme deficiencies, leading to varying levels of phenylalanine accumulation in the body. Examples of non-PKU hyperphenylalaninemias include tetrahydrobiopterin (BH4) deficiency, dihydropteridine reductase (DHPR) deficiency, and sepiapterin reductase (SR) deficiency.
2. Transient Hyperphenylalaninemias: Unlike the permanent nature of other hyperphenylalaninemias, transient hyperphenylalaninemias are temporary conditions. They occur due to factors such as prematurity, liver disease, or certain medications. In these cases, high phenylalanine levels are observed but return to normal as the underlying cause is resolved.
3. Variant Hyperphenylalaninemias: This group encompasses rare forms of hyperphenylalaninemias caused by specific gene mutations. Examples include hyperphenylalaninemia due to GTP cyclohydrolase I (GTPCH) deficiency and hyperphenylalaninemia due to pterin-4-alpha-carbinolamine dehydratase (PCD) deficiency. These variants may present with similar symptoms to PKU, but genetic testing is required for accurate diagnosis.

It is important to note that the symptoms and severity of other hyperphenylalaninemias can vary widely. Some individuals may be asymptomatic, while others may experience intellectual disability, developmental delays, seizures, or behavioral problems. Early detection and diagnosis through newborn screening programs enable timely intervention and management.

While treatment options for hyperphenylalaninemias are beyond the scope of this article, it is crucial to emphasize that each subtype requires specialized care and dietary management. Phenylalanine-restricted diets, supplemented with special formulas, are often prescribed to prevent phenylalanine buildup and support healthy growth and development.

In conclusion, hyperphenylalaninemias encompass a range of genetic disorders characterized by elevated phenylalanine levels in the blood. Apart from phenylketonuria (PKU