Dominant PRA is an eye disorder that affects English Mastiffs and Bull Mastiffs. It is a form of progressive retinal atrophy (PRA) that causes cells of the eye to deteriorate over time eventually leading to complete blindness. Typically, affected dogs show symptoms of the disease starting at approximately 2-3 years of age however, symptoms including night-blindness have been observed in puppies as young as 6 weeks. Progression of the disease is fairly quick with most affected dogs suffering complete blindness within 1-2 years from the onset of symptoms. This particular type of PRA seen in the Mastiff breeds is a dominant condition which means a dog only need inherit one copy of the mutation to be affected by the disease.

• English Mastiff
• Bullmastiff

A (CLEAR/NORMAL): These dogs have two copies of the normal gene and will neither develop PRA-D nor pass this mutation to their offspring.

B (CARRIER/AFFECTED): These dogs have one copy of the normal gene and one copy of the mutation associated with this disease. They will develop PRA-D and will, if bred, pass the mutation to 50% of its offspring, on average.

C (AT RISK/AFFECTED): These dogs have two copies of the mutation associated with PRA-D which results in visual deterioration and eventual blindness.