Why does my dog listed as At-Risk despite having only one copy of the Primary Lens Luxation (PLL) variant?

The ADAMTS17 variant is responsible for an increased risk of Primary Lens Luxation (PLL). This causative variant has an additive inheritance type and not a recessive mechanism of inheritance. So while dogs with one copy of the variant have a higher risk than dogs with two healthy alleles at ADAMTS17, their risk is much lower than a dog with two copies of the variant. 

The actual risk associated with having one copy of this variant appears to vary by breed.

Because dogs with one copy of the variant can still develop Primary Lens Luxation (even if this risk is low), we use the term "At-Risk" instead of "Carrier."