Glutaric Aciduria Type 1 (GA-1) overview
Causes & genetic inheritance of Glutaric Aciduria Type 1 (GA-1)
Symptoms of Glutaric Aciduria Type 1 (GA-1)
GA-1 dietary management and treatment
Living with GA-1
Glutaric Aciduria Type 1 (GA-1) overview
What is Glutaric Aciduria Type 1 (GA-1)?
Glutaric aciduria type 1 (also known as GA-1) is a rare inherited disorder of protein metabolism. It is a rare metabolic disorder. In countries where newborn screening is available, GA-1 can be diagnosed in the first few days of life. People with GA-1 inherit faulty genes that affect their body's ability to metabolise and break down the amino acids lysine and tryptophan.
If lysine and tryptophan are not processed correctly by the liver, the by-products of the malfunctioning protein breakdown process (mainly glutaric acid, hence the name of the disorder) accumulate to toxic levels in the body. Left untreated, this toxic build-up of glutaric acid and other toxins will lead to neurological damage, low intellectual development, and neurological underdevelopment. People with Glutaric aciduria type 1 are also at a higher risk of metabolic decompensation, where the body cannot maintain its normal biochemical balance during health crises (e.g., febrile infection, vomiting, diarrhoea, vaccination reactions, and surgeries). These metabolic decompensations should be counteracted by early emergency treatment from specialized metabolic healthcare facilities to prevent further neurological impairment. There is no cure for GA-1. However, the disorder can be effectively managed with medication, metabolic products and a low-protein diet to control the intake of natural dietary protein.
Causes & genetic inheritance of Glutaric Aciduria Type 1 (GA-1)
Glutaric aciduria type 1 is an inherited disorder passed down from parents. GA-1 is an autosomal recessive condition. This means that although healthy, both the father and mother each carry a faulty gene affecting amino acid metabolism.
If both parents are carriers of this genetic anomaly, that affects the enzyme glutaryl-CoA dehydrogenase, which degrades lysine and tryptophan, there is a 1 in 4 (25%) chance with each pregnancy that their child will have GA-1. However, because the gene change is uncommon, the overall chance of a child being born with GA-1 is low.
This enzyme deficiency leads to the accumulation of harmful substances in the body. While GA-1 is the focus, it's worth noting other types of Glutaric Aciduria, such as Glutaric Acidemia Type II (GA-2). Understanding the distinction between acidemia vs acidosis is also important in metabolic discussions, as acidemia refers to an increase in blood acidity due to accumulated organic acids, while acidosis is a broader term for any condition that causes excess acid in the body.
Symptoms of Glutaric Aciduria Type 1 (GA-1)
Without dietary management, the symptoms of GA-1 can be severe. Due to the body’s inability to completely process the amino acids lysine, and tryptophan, the by-products of the insufficient breakdown of amino acids accumulate in toxic levels in the body. Common symptoms include:
- Learning and intellectual impairment
- Neurological impairment (brain damage)
- Heightened risk of metabolic decompensation during health crises such as febrile infection, vomiting, diarrhoea, vaccination reactions, and surgeries
Untreated GA-1 can lead to neurological damage, low intellectual development, and neurological underdevelopment. Recognising early signs and obtaining early detection through newborn screening is crucial to prevent severe neurological complications.
GA-1 dietary management and treatment
Adherence to a lifelong low-protein diet is crucial for people with GA-1.
The role of Food for Special Medical Purposes and protein substitutes
The GA-1 diet is specifically designed to limit lysine intake, which helps keep blood lysine and tryptophan levels low. The diet mainly consists of low-protein foods, protein substitutes, and other supplements as prescribed by a specialist healthcare professional to ensure the body gets enough of the other essential amino acids without providing additional lysine. These lysine-free protein substitutes are vital to ensure adequate protein, energy, vitamins, and minerals for growth and normal body function, enabling a better quality of life for GA-1 patients. Accuracy and consistency in following the diet are vital for healthy development.
Medical intervention
GA-1 treatment involves a comprehensive approach including dietary management and other interventions. During periods of metabolic stress (like illness or fasting), emergency protocols are crucial to prevent metabolic crises and neurological damage. Supplements such as L-carnitine may also be prescribed, as carnitine deficiency can sometimes be a concern in GA-1 due to accumulated metabolites.
GA-1 diet and foods to avoid
A low-lysine diet is the cornerstone of GA-1 management. This protein-restricted diet means carefully controlling the intake of lysine and tryptophan.
Guidance on foods high in lysine to avoid is critical. Generally, foods rich in protein are high in lysine. These include:
- Meat, poultry, and fish
- Dairy products like milk, cheese, and eggs
- Certain nuts and seeds
- Some legumes
Specialised medical food is essential to meet nutritional needs while carefully controlling lysine and tryptophan intake.
Living with GA-1
Living with GA-1 requires constant vigilance and commitment to a low-protein diet supported by regular medical check-ups. It’s essential to have ongoing support from a dietitian specialising in metabolic disorders to help manage a low-protein diet and ensure the correct amount of protein substitute is prescribed to meet protein requirements.GA-1 presents different challenges throughout life. As a baby, child, teenager, and adult, the needs and experiences of a person diagnosed with GA-1 will vary. For example, babies need a special infant feed in addition to breast milk and/or standard infant formula; children must learn to cope with dietary restrictions; teenagers may face social pressure; and adults must manage their diet while living an independent, busy lifestyle.
Regular check-ups with a doctor and/or dietitian are crucial to ensure ongoing effective management of the disorder as the body's needs change over time. By following a low-protein diet and adhering to medical protocols, people with GA-1 can live healthy and full lives. For inspiration, delicious low-protein recipes are available.
