Imerslund-Gräsbeck syndrome

What else is it called?

Imerslund-Gräsbeck syndrome is also known as: 

  • Familial megaloblastic anaemia  
  • Selective cobalamin malabsorption with proteinuria  
  • Defect of enterocyte intrinsic factor receptor  
  • Enterocyte cobalamin malabsorption  
  • Juvenile pernicious anaemia with proteinuria due to selective intestinal malabsorption of vitamin B12 
  • Megaloblastic anaemia 1  
  • IGS 
  • Pernicious anaemia  
  • Gräsbeck-imerslund disease

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What causes it?

This disease is caused by a problem in the AMN or the CUBN gene. The AMN gene provides the blueprints for a protein called amnionless and the CUBN gene provides the instructions to make the protein known as cubilin. These two proteins are important in the uptake of vitamin B12, which is very important for your health. Vitamin B12 is used to create DNA and proteins and is also used to create energy for your body and maintain your brain and spinal cord.

How common is it?

The estimated prevalence of this disorder is less than 6:1,000,000. However there are around 300 cases that have been published worldwide. This disorder seems to be more prevalent in eastern Mediterranean countries. In finland and Norway the prevalence is around 1:200,000. 

What are the signs and symptoms?

The disorder begins to manifest during childhood. People with this disorder begin to experience non-specific health problems at first such as: 

  • Failure to thrive 
  • Recurrent gastrointestinal  
  • Respiratory infections  
  • Pallor  
  • Fatigue  

The signs and symptoms of this disease are: 

  • Confusion 
  • Dementia  
  • Malabsorption of vitamin B12 
  • Vitamin B12 deficiency  
  • Megaloblastic anaemia  
  • Pins and needles feeling (Paresthesia)  
  • Proteinuria (high protein level in urine)  
  • Sensory impairment  

People affected with this disorder also have anaemia while others may have mild proteinuria with no signs of kidney disease. In some cases people may also have mild neurological damage with urinary tract abnormalities.

How is it diagnosed?

This disorder can be diagnosed after a series of tests are performed. The first test is for cobalamin deficiency, then other causes of vitamin B12 malabsorption must be ruled out. Then a diagnosis can be made using genetic testing of the AMN and CUBN genes. The presence of proteinuria is a strong indicator of IGS.  

Can it be treated?

Unfortunately, there isn’t a cure for this disorder however, there is lifelong treatment that can be given. The disorder is treated by giving life-long treatment of the vitamin B12. IGS is also treated by giving intramuscular injections of cobalamin. 


Do my family need to be tested?

IGS is an autosomal recessive inherited metabolic disorder. Every human being needs two copies of the AMN and CUBN gene in order for the amnionless and cubilin proteins to be made correctly. When both of these gene copies are made incorrectly then IGS will develop. A person will inherit IGS if both of their parents carry at least one defective form of the AMN and CUBN gene, these people are called carriers. They do not have the disorder because they have at least one working form of the gene.  

In the event that both parents are carriers of the defective genes then the risk of the disorder during pregnancy is:  

  • 25% that the child will not develop IGS and will not be a carrier 
  • 25% that the child will develop IGS 
  • 50% that the child will not develop IGS and will be a carrier 

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