Lysinuric Protein Intolerance
What else is it called?
- Congenital lysinuria
- Hyperdibasic aminoaciduria
- LPI – Lysinuric protein intolerance
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What causes it?
Lysinuria protein intolerance [LPI] is an autosomal recessive condition in which the body cannot process specific amino acids. These amino acids being lysine, arginine, and ornithine. Due to the body’s inability to digest these foods, after ingestion of high protein-based meals nausea and vomiting may proceed this. A lack of these proteins may incur problems with the connective tissue within the body such as skin
Mutations in the SLC7A7 gene are believed to cause this condition, these gene are responsible for making the protein, y+L amino acid transporter 1. Many of these proteins are involved in regulating the urea cycle which is how urine in metabolised.
How common is it?
Current research suggests that this metabolic condition impacts 1 in 60,000 newborns in the region of Finland and 1 in 57,000 in regions of Japan. Instances in other areas are less known, this may be due to the rarity of this condition. Due to this rarity, it is unclear whether this condition is more common in males or females or with specific ethnicities.
What are the signs and symptoms?
Symptoms can appear in late infancy once a child has been weaned onto solid foods full of protein.
- Enlarged spleen
- Impaired immune function
- More exposure and potential risk to bone problems such as osteoporosis
- End stage renal disease
- Failure to thrive
- Lung and kidney dysfunction
Occasionally, individuals also develop problems with their lungs such as pulmonary alveolar. A lack of certain proteins within the body may also see an increase in ammonia levels within the body which may pose a risk to an individual’s health.
How is it diagnosed?
LPI can be diagnosed by noticing the expression of physical symptoms related to LP. It may also be queried if you have a family history of this condition. This condition can be accurately diagnosed by genetic testing for a SLC7A7 gene mutation. Your health care professional will advise you to have genetic testing if they believe that you may have this condition.
Can it be treated?
Treatment is usually aimed at avoiding high protein meals containing lysine, arginine, and ornithine due to the likelihood that this will incur in symptoms. You will know how much protein is going to causes an onset of problems though diagnosis of this metabolic condition. Medication can also be prescribed to help prevent the build-up of nitrogen and ammonia within the body.
Do my family need to be tested?
LPI can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier.
If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.
If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.
Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inherited LPI. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own.
If you have previously had a child with LPI and go on to have further children, their New-born Screening test should be carried out within 24-48 hours of birth.