Carnosinaemia

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The gene associated with this condition is unknown. However, carnosinase is the enzyme responsible for carnosine breakdown and is known to be found in the brain and the blood. The role of carnosinase (enzyme) is to breakdown carnosine into two basic elements. Individuals with the condition, Carnosinaemia usually have abnormally high levels of carnosine in their urine and abnormally low levels of the enzyme carnosinase in their blood.  

Carnosinaemia is a very rare inherited disorder, affecting males and females equally. Approximately 30 individuals have been reported with this condition world-wide.  

The signs and symptoms of this condition can occur as early as in children under the age of one year. Symptoms may include: 

•  drowsiness  
• seizures/ myoclonic seizures (a brief shock-like jerks of a muscle or group of muscles, the person is usually awake) 
• slow growth  

• low muscle tone 
• motor delays  
• delayed intellectual development  

 Around the age of 2 years, children with the condition show a degree of intellectual deficit (below average intelligence) which can cause intellectual disabilities and developmental regression (when a child fails to progress along a relatively normal development rate).  

Other symptoms of children with this condition include:  

 congenital myopathy (muscle weakness) 

• Abnormal EEG (Electroencephalogram – a test that spots electrical activity in the brain) test results 

 Some patients reported with this condition show no or very few symptoms.  

Diagnosis of this condition includes testing the levels of amino acids in the blood and/or urine which will show abnormally high levels of carnosine and anserine. Specialized blood tests will show very low activity of the enzyme carnosinase in the blood.  

A diagnosis is confirmed based on amino acid analysis of blood plasma and urine after removing meat from the diet.  

The treatment for this condition is symptomatic and supportive as there has been no effective drug treatment so far. The aim of this treatment is to manage and alleviate individual symptoms and provide support for the patients and their families.  

 Genetic counselling is recommended for people with this condition and their families.  

Carnosinaemia is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.  

 The pattern of inheritance of Carnosinaemia is autosomal recessive. This means that carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with Carnosinaemia are carriers.   

When both parents are carriers, the risk to the baby in each pregnancy is  

•  25% chance (1 in 4) of developing the condition  
•  50% chance (1 in 2) for the baby to be a carrier of the condition  
•  25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier  

 Genetic counselling can be requested to get a full explanation.

References are available on request. Please email contact@metabolicsupportuk.org or call 0845 241 2173  [Resource Library No: CAP085].