Test Results (PRA-PRCD) (PLL) (DM)
Chinese Crested Progressive Rod Cone Degeneration (PRA-PRCD)
CLEAR/NORMAL: These dogs have two copies of the normal gene and will neither develop PRA-PRCD nor pass this mutation to their offspring.
CARRIER/NOT AFFECTED: These dogs have one copy of the normal gene and one copy of the mutation associated with this disease. They will not develop PRA-PRCD and will, if bred, pass the mutation to 50% of its offspring, on average.
AT RISK/AFFECTED: These dogs have two copies of the mutation associated with PRA-PRCD which typically results in complete blindness for most breeds.
Chinese Crested Primary Lens Luxation (PLL)
CLEAR/NORMAL: These dogs have two normal copies of DNA. Research has demonstrated clear dogs will not develop PLL as a result of the mutation, although it is possible they might develop PLL due to other causes, such as trauma or the effects of other, unidentified mutations.
CARRIER/NOT AFFECTED: These dogs have one copy of the mutation and one normal copy of DNA. Research has demonstrated that carriers have a very low risk of developing PLL. The majority of carriers do not develop PLL during their lives but a small percentage do. Current estimates are that between 2% – 20% of carriers will develop the condition.
AT RISK/AFFECTED: These dogs have two copies of the mutation and will almost certainly develop PLL during their lifetime. It is advised that all genetically affected dogs have their eyes examined by a veterinary ophthalmologist every 6 months, from the age of 18 months, so the clinical signs of PLL are detected as early as possible.
Canine Degenerative Myelopathy (DM)
Genetic testing of the SOD1 gene in Chinese crested dogs will reliably determine whether a dog is a genetic Carrier of degenerative myelopathy. Degenerative Myelopathy is inherited in an Autosomal Recessivemanner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the SOD1 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms may not appear until adulthood and some at-risk/affected dogs do not develop the disease, genetic testing should be performed before breeding. Until the exact modifying environmental or genetic factor is determined, genetic testing remains the only reliable way to detect neurological disease associated with this mutation prior to death. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Chinese crested dogs that are not carriers of the mutation have no increased risk of having affected pups.Breed-Specific Information for the Chinese Crested
The Mutation of the SOD1 gene associated with degenerative myelopathy has been identified in the Chinese crested. The overall frequency of this disease in the breed and approximate age of disease onset are currently unreported for the Chinese crested. However, in one study of 53 Chinese crested dogs tested, 24.5% were carriers of the mutation.