Intestinal Cobalamin Malabsorption (CUBN gene, Komondor)

Intestinal cobalamin malabsorption, also known as Imerslund-Gräsbeck syndrome, is a rare genetic condition that affects the body's ability to absorb vitamin B12 (cobalamin) in the small intestine.


Symptoms of intestinal cobalamin malabsorption usually appear between 6 and 12 weeks of age and include weakness, growth retardation, vomiting, diarrhea, liver disease, anemia and decreased white blood cell count. An increase of certain proteins in the urine or proteinuria is also characteristic.

Disease Management

In case your puppy shows any symptoms you should visit your veterinarian for evaluation. Affected dogs need cobalamin supplements for life, which causes remission of the disease in most treated animals.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Cobalamin or vitamin B12 is an essential micronutrient that is important in protein metabolism. This vitamin is absorbed in the ileum of the small intestine by the cubam molecular complex which is expressed in the cells of the intestinal epithelium and kidneys and is composed of cubilin (CUBN) and amnionless (AMN) subunits. Affected dogs are unable to produce adequate amounts of CUBN. Here we analyze the c.8746+1G>A variant in the CUBN gene that is responsible for cobalamin malabsorption in dogs of the Komodor breed. Other disease-causing mutations in CUBN have been described in Beagle and Border Colie (not analyzed here).

Most affected breeds

  • Beagle
  • Border Collie
  • Komondor


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