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Cystinuria is known to be an autosomal recessively inherited disease in Newfoundland and Labrador retriever dogs, and there is a DNA test available for those breeds that can determine if they are carriers, affected or genetically clear of the disease.  In Mastiffs Cystinuria is a more complex disease and the mode of inheritance is not fully understood.  We do know that Cystinuria in Mastiffs is fairly common and many dogs are affected from various lines.  Not all Mastiffs that test positive on the nitroprusside urine spot test will form stones and it is not understood why some Mastiffs form cystine stones and others do not.  We also do not understand why in Mastiffs the males show clinical and biochemical signs of the disease and females do not.  Mastiffs do NOT have the same gene mutations for Cystinuria that is in Newfoundland & Labrador Retriever dogs. We need your help with research participation, data collection and fund raising in order to solve this puzzle, learn the mode of inheritance in Mastiffs, better understand the environmental and metabolic influences that trigger the expression of clinical symptoms of Cystinuria, and develop a DNA test for our breed. Cystinuria in Mastiffs appears to mainly affect males, which has made us suspicious of an X linked form of inheritance, or sex-limited expression of the disease. Through current pedigree analysis, there is no direct evidence that Cystinuria in Mastiffs is inherited in any simple form, including simple x-linked recessive inheritance. Genetic studies continue, unfortunately we are not in a position to label Cystinuria in Mastiffs with any given simple mode of inheritance. At this time we have to treat Cystinuria as a disease with complex inheritance. This means that multiple factors influence which dogs are affected with the disease, including genetics (the effects of one or more genes) and environmental influences.Cystinuria is often described as running in certain lines or pedigrees, which basically means that more than one dog in the family, has the condition. When relatives of Cystinuria positive dogs are screened for Cystinuria using the nitroprusside urine test, we have seen cases where one or more close relatives also test positive.  By having multiple family members test positive, and having a higher disease incidence in Mastiffs than in other breeds, it is apparent that Cystinuria does have an inherited component that can be passed down from parent to offspring.By studying Mastiffs that test positive for Cystinuria, there is some evidence that metabolic or environmental factors can influence the expression of the disease.  As previously mentioned, it is extremely important that the owners and breeders of Cystinuria positive Mastiffs share, with the researchers, all the information they can on their dogs to help them solve this very complicated puzzle.As the researchers at UPenn are getting more families of Mastiffs participating in the research, continue their gene mapping & pedigree analysis, and observe environmental factors that may contribute to the expression of the disease, they are seeing that it is definitely much more complex than they originally hoped and certainly much more complex than the situation in Newfoundlands and Labrador Retrievers.  Again, they need participation from Mastiff owners and breeders in order to fully understand Cystinuria in Mastiffs, to help them define the actual mode of inheritance, and to develop a DNA test for Cystinuria in our breed.

Articles that describes the various types of inheritance and genetics:


Various Ways That Genetic Conditions Can Be Inherited·  
Reduced Penetrance and Variable Expressivity·
What are complex or multifactorial disorders?·
Factors Affecting Gene Expression·
Unusual Aspects of Inheritance·
Huntington Disease – Genetics

Until we know the mode of inheritance for Cystinuria in Mastiffs and until we have a DNA test for this disease in our breed, please utilize the Nitroprusside Urine screening test that is offered through the PennGen Laboratory.  Please test all of your Mastiffs and as many of their offspring and other close relatives as you can and participate in the research at UPenn.  The more families with multiple generations that can be Cystinuria tested, the sooner we’ll know the exact mode of inheritance.Please also keep in mind that the more blood samples we have, the faster the team at UPenn will get their work done and we will be on our way to having the tools to eliminate another genetic problem from our beloved breed. We are closer now than we have ever been in reaching some important conclusions and being able to take the necessary steps to eliminate this disease from Mastiffs. 


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