Genetics and characteristics
Elliptocytosis is a genetic blood disorder in which normally round red blood cells appear to be oval-shaped and can have serrated edges. The disease has been previously described in humans but it can also affect dogs, mostly mixed breeds. Change in the erythrocytes reduces cellular deformability and mechanical stability causing the lack of their normal biological function in carrying oxygen through the body. In most cases, it can be asymptomatic, but it can also be the cause of severe hemolytic anemia and potentially lead to death. Canine hereditary elliptocytosis results from qualitative or quantitative defects in erythrocyte membrane proteins, in this case, a specific mutation within the beta spectrin. This mutation alters the molecular structure of the erythrocyte membrane, leading to impaired spectrin self-association and elliptocyte formation.
The mode of inheritance for this type of Elliptocytosis mostly found in mixed breed dogs is still yet to be defined. There are two possible modes – an autosomal recessive one and an autosomal dominant one with incomplete disease penetrance. The latter is more likely to be correct meaning dogs with two copies of the mutated SPTB gene will develop the disease and dogs that carry one mutated gene may develop a milder form of the disease or be asymptomatic. Early genetic testing can help identify affected dogs that carry the mutation and prevent their further breeding by proper selection of mating pairs.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
AFFECTED HETEROZYGOTE |
Tested mutation was detected in animal with „affected heterozygote“ result. Animal tested as affected heterozygote has one wild-type and one mutation allele, it is in heterozygous state. It is likely to develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
**Penetrance of tested mutation, and potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Di Terlizzi, R., Gallagher, P. G., Mohandas, N., Steiner, L. A., Dolce, K. S., Guo, X., Wilkerson, M. J., Stockham, S. L. (2009). Canine elliptocytosis due to a mutant beta-spectrin. Veterinary clinical pathology, 38(1), 52–58. https://doi.org/10.1111/j.1939-165X.2008.00092.x
Mills, J. N., Marsden, C. A. (1999). Presumed hereditary elliptocytosis in a dog. Australian veterinary journal, 77(10), 651–652. https://doi.org/10.1111/j.1751-0813.1999.tb13153.x