Introduction
The AKC Canine Health Foundation (CHF) has long supported the health of all dogs by funding scientific research and sharing trusted health information. Through strong partnerships with breed Parent Clubs, CHF helps researchers explore inherited conditions that affect specific breeds—leading to better diagnostics, treatments, and breeding practices.
One example of this collaboration in action is the recent progress made in understanding a heritable condition in Portuguese Water Dogs. For years, breeders noticed puppies with unusually small eyes, slow growth, and other concerning symptoms. Known informally as Puppy Eye Syndrome, the condition was difficult to diagnose and manage. Thanks to CHF-funded research, the genetic cause has now been identified, and a reliable test is available to help breeders reduce the risk of affected litters.
Key Points
- Microphthalmia Syndrome causes small eyes, anemia, stunted growth, and other health issues in Portuguese Water Dogs.
- The disease is inherited in an autosomal recessive pattern—both parents must carry the mutation for a puppy to be affected.
- Researchers at Penn Vet identified a mutation on chromosome 4 as the cause.
- A genetic test is now available through PennGen to help breeders avoid producing affected puppies.
- As of May 2024, only 0.7% of tested dogs had two copies of the mutation, showing the test’s success in reducing disease incidence.
Challenge Background
Since the 1980s, Portuguese Water Dog breeders noticed some puppies were born with unusually small eyes and failed to thrive. These puppies were often dismissed as “poor doers,” but breeder Linda Carey suspected a deeper issue. Affected puppies showed signs like blindness, abnormal appetite, and internal bleeding due to low platelet counts. The condition, originally called Puppy Eye Syndrome, was poorly understood and lacked a clear diagnostic or prevention strategy.
This uncertainty made breeding decisions difficult and heartbreaking, as even healthy-looking parents could produce sick puppies. The need for a scientific explanation and a reliable way to prevent the disease was urgent.
The Breakthrough
With support from the AKC Canine Health Foundation, the Portuguese Water Dog Club of America, and the Portuguese Water Dog Foundation, researchers at Penn Vet led by Dr. Margret Casal investigated the condition (CHF Grant 02403-MOU: Microphthalmia and Delayed Growth Syndrome in the Portuguese Water Dog). They discovered that Microphthalmia Syndrome is caused by an insertion mutation on chromosome 4, which disrupts normal protein production and degradation.
The disease follows an autosomal recessive inheritance pattern, meaning a puppy must inherit two copies of the mutated gene—one from each parent—to be affected. Researchers developed a genetic test that identifies carriers and affected dogs, allowing breeders to make informed decisions and avoid producing puppies with the syndrome.
Impact & Next Steps
The genetic test is now available through PennGen, and its impact is already visible. As of May 2024, only 0.7% of tested Portuguese Water Dogs had two copies of the mutation, showing a significant reduction in disease prevalence.
This breakthrough empowers breeders to protect future generations of dogs, and it sets a precedent for tackling other heritable diseases. Continued collaboration and research will help ensure all dogs live longer, healthier lives. Dog owners and breeders are encouraged to support ongoing research and use available genetic tools to improve canine health.
Thanks to the dedicated efforts of the Portuguese Water Dog Club of America, the Portuguese Water Dog Foundation, CHF, and Penn Vet researchers, we have a firm understanding of Microphthalmia Syndrome in the PWD and breeders are using this knowledge to produce healthier dogs. Working together, we will continue to help all dogs live longer, healthier lives. Join us at akcchf.org.
