*Note: A mutation present in the ATP7A gene has been shown to decrease copper accumulation in dogs that have inherited one or two copies of the ATP7B gene mutation associated with copper toxicosis (Labrador retriever type). The effect of the ATP7A gene mutation in preventing increases in total body copper is more effective in male dogs, though the mutation in ATP7A is not completely protective in either sex. Because there are multiple factors contributing to copper toxicosis, dogs inheriting the ATP7A mutation may still be at risk of copper toxicosis if they have also inherited the ATP7B gene mutation or other unknown mutations.

Genetic testing of the ATP7A gene in Labrador retrievers will reliably determine whether a dog is a genetic carrier of the copper toxicosis modifier (Labrador retriever type). The copper toxicosis modifier (Labrador retriever type) decreases the risk of excessive copper accumulation in an X-Linked incomplete dominant manner meaning that male dogs that are at risk for copper toxicosis due to inheritance of the associated mutation in the ATP7B gene only need to inherit one copy of the semi-protective ATP7A gene mutation to be at a decreased risk of disease. However, female dogs that are at risk for copper toxicosis due to inheritance of the associated ATP7B gene mutation and carriers of one copy of the semi-protective ATP7A mutation, may have a higher risk of developing copper toxicosis than male carriers due to the presence of another normal copy of the ATP7A gene in female dogs. Female dogs that inherit two copies of the ATP7A mutation are more protected than those that inherit only one copy of the ATP7A mutation. In addition, male dogs inheriting one copy of the ATP7A mutation tend to accumulate less copper when inherited with the ATP7B mutation than their female counterparts. In general, dogs that are not at risk for copper toxicosis (Labrador retriever type) because they did not inherit the ATP7B gene mutation are not affected positively or negatively when they inherit one or two copies of the ATP7A gene mutation.

There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.