What else is it called?
- Hyperglycinemia with ketoacidosis and leukopenia
- Ketotic glycinemia
- Ketotic hyperglycinemia
- PCC deficiency
- Propionic acidemia
- Propionyl-CoA carboxylase deficiency
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What causes it?
PA stands for Propionic Acidaemia. It is an inherited metabolic condition.
PA affects the way your baby breaks down protein. Many foods contain protein. The body needs protein for growth and repair.
Protein is broken down into amino acids (building blocks of protein) by enzymes (which are like chemical scissors). Enzymes then further break the amino acids into smaller parts.
In PA, the body lacks an enzyme called propionyl-CoA carboxylase. This means the body is unable to break down four amino acids (protein). As a result, there is a build-up of a chemical called propionic acid. This causes too much propionic acid and other chemicals in the blood and too many abnormal chemicals in the urine.
Propionic acid also comes from:
- The breakdown of fatty acids. The body will use these for energy when it has gone a long time without food
- Gut bacteria
How common is it?
PA occurs in approximately 1 in 50,000 to 1 in 100,000 births worldwide. This may increase with milder cases being detected by newborn screening. Incidence is as high as 1 in 2,000 to 1:5,000 in Saudi Arabian populations.
What are the signs and symptoms?
Symptoms commonly start in the first few days of life. Symptoms include:
- poor feeding
- dehydration (lack of body fluids)
- floppy baby
- excessively sleepy
- rapid breathing
The effects of PA quickly become life-threatening if untreated.
The build-up of harmful chemicals can damage the brain and heart and cause problems with other organs. It may cause delays to normal development like walking and talking.
If the body does not receive enough food e.g. during illness or the body has gone without food for too long, there may be a shortage of energy supply. This causes catabolism which is a break-down of body protein and can lead to a metabolic crisis.
In a metabolic crisis there is a build-up of propionic acid and other toxic chemicals such as ammonia
- It is usually triggered by childhood illnesses e.g. vomiting and diarrhoea or fasting for too long
- There should be no delay in treatment
- Avoidance of a metabolic crisis is essential
In PA, it is important that enough protein is given for growth…but not too much as toxic chemicals will be made.
How is it diagnosed?
PA is diagnosed by measuring chemicals containing propionic acid in the blood and urine. It can also be diagnosed by looking at enzyme levels and at the body’s genes.
Can it be treated?
PA is managed with the following:
- A protein restricted diet
- Ensuring a sufficient energy supply
- Regular feeding
- Carnitine medication
- Antibiotics to control gut bacteria
- Other medications may be necessary
Tube feeding may be necessary to give regular feeds. This will ensure energy, nutrient and fluid needs are met and can help to reduce the production of abnormal chemicals.
During any childhood illness, an emergency regimen is given. This is to ensure sufficient energy
supply to prevent the build-up of harmful chemicals that cause a metabolic crisis.
- Stop all protein in food & drink
- Start the emergency regimen. This is made up of glucose polymer
- Continue medication as prescribed
- Always take full amounts of emergency feeds as prescribed
- If symptoms continue and/or you are worried, go immediately to the hospital
- Regularly update your metabolic team
It is imperative that emergency feeds are started promptly and there are no delays in management.
PA is monitored by:
- Frequent blood tests to check amino acids, nutrient and chemical levels
- Height and weight
- Developmental checks
Diet and medications are adjusted according to age, weight and blood chemical levels
Take home messages:
- PA is a serious inherited metabolic disorder that can lead to severe problems
- The condition is managed with a protein restricted diet, regular feeding and medications
- Remember, during illness, it is imperative that emergency feeds are started promptly, followed strictly and there are no delays in management
- Always ensure you have a good supply of your dietary products and that they are in date.
- Your dietary products are prescribed. These are obtained via a pharmacy or home delivery.
- Always ensure you have your emergency feed products and a written emergency plan.
- Medications to control fever should be given as normally recommended – always keep supplies available.
Do my family need to be tested?
Humans have chromosomes composed of DNA. Genes are pieces of DNA that carry the genetic instruction. Each chromosome may have several thousand genes.
The word mutation means a change or error in the genetic instruction. We inherit particular chromosomes from the egg of the mother and sperm of the father.
The genes on those chromosomes carry the instruction that determines characteristics, which are a combination of the parents. PA is an inherited condition. There is nothing that could have been done to prevent your baby from having PA.
Everyone has a pair of genes that make the propionyl-CoA carboxylase enzyme. In children with PA, neither of these genes works correctly. These children inherit one non-working PA gene from each parent.
Parents of children with PA are carriers of the condition. Carriers do not have PA because the other gene of this pair is working correctly.
When both parents are carriers, in each pregnancy the risk to the baby is as follows:
- 25% chance (1 in 4) of PA
- 50% chance (1 in 2) for the baby to be a carrier of PA
- 25% chance (1 in 4) for the baby to have two working genes and neither have PA or be a carrier
This information is from the TEMPLE Guides which have been adapted by the Dietitians Group of the British Inherited Metabolic Disease Group (BIMDG) and is based on the original TEMPLE written by Burgard and Wendel. The TEMPLE Guides are supported by Nutricia. Dated February 2017.
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