How can an inborn error of metabolism affect the developing brain?

An inborn error of metabolism can severely impact the developing brain primarily through the accumulation of toxic substances. When a genetic defect results in a missing or dysfunctional enzyme, a metabolic pathway becomes blocked, leading to a deficiency in essential products and the buildup of otherwise normal metabolites that become toxic at high concentrations.123

This accumulation often manifests as encephalopathy, characterized by abnormal brain function and structure. While the exact biochemical mechanisms are still being studied, this toxicity is believed to disrupt critical processes such as:1

• Brain energy metabolism: Interfering with the fuel supply required for development.1
• Neurotransmitter synthesis: Altering the chemical signaling necessary for brain function.1
• Myelin formation: Impairing the development of the insulating material around neurons.1

If left untreated, these metabolic imbalances can lead to severe consequences, including intellectual disability, seizures, and developmental delays. Fortunately, early detection through newborn screening allows for interventions—such as specialized diets or medical treatments—that can often prevent brain injury and support normal neurological development.123