Breeds Affected: Australian Shepherd
Samples Accepted: Blood, Buccal Swab
Disease Information: Imerslund-Gräsbeck Syndrome (IGS) is also known as Intestinal Cobalamin Malabsorption or Megaloblastic Anemia 1. Affected animals are unable to absorb cobalamin (Vitamin B12) from their diet and pups are usually diagnosed between 6-12 weeks of age. Symptoms include failure to thrive, anorexia, neutropenia, nonregenerative anemia and homocysteinemia.
Inheritance Information: IGS is autosomal recessive, meaning that animals with two copies of this allele will be affected. Animals with one copy of the gene will be clinically-normal carriers.
The possible genotypes are:
N/N The dog is normal, and cannot produce affected offspring.
N/igs The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/igs carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
igs/igs The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to an N/igs carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/igs x N/N) without any risk of producing affected offspring. The offspring should be tested before breeding to determine if they are carriers or normal.
– Breeding two carriers (N/igs x N/igs) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (igs/igs) should not be used for breeding.
Test information: This mutation test identifies a single base change in exon 1 of the AMN gene.
He, Q., Madsen, M., Kilkenney, A., Gregory, B., Christensen, E.I., Vorum, H., Højrup, P., Schäffer, A.A., Kirkness, E.F., Tanner, S.M., de la Chapelle, A., Giger, U., Moestrup, S.K., Fyfe, J.C.: Amnionless function is required for cubilin brush-border expression and intrinsic factor-cobalamin (vitamin B12) absorption in vivo. Blood 106:1447-53, 2005. Pubmed reference: 15845892. DOI: 10.1182/blood-2005-03-1197.
Further information is available at the Online Mendelian Inheritance in Animals website.