Von Willebrand's Disease Type 1 in Shetland Sheepdogs

The genetic result and the clinical outcome are related but not identical, and understanding the gap between them is the single most useful thing this page can offer a Sheltie owner or breeder looking at a panel report.

Type 1 von Willebrand's disease is unusual among inherited conditions in how loosely its genetic status predicts clinical severity. Unlike a straightforward recessive condition where two copies of a variant reliably produce a defined, consistent problem, Type 1's clinical expression is genuinely variable between individual dogs, even within the same breed and the same genetic result category. Some genetically affected dogs have von Willebrand factor levels low enough to show real bleeding tendency; others have levels that sit close enough to normal that they show no clinical signs at all and would only be caught by the DNA panel, not by a functional blood test taken on an ordinary day.

This is exactly why responsible pre-surgical screening in a breed where the variant is present increasingly uses both tools rather than either alone. The DNA panel establishes genetic status permanently and does not need repeating, since it cannot change with age or health status. A functional test, either a bleeding time assessment or a direct measurement of von Willebrand factor activity, captures how the dog's clotting is actually performing at that point in time, which is what a surgical team actually needs to plan around. A dog can be DNA-affected with a currently reassuring functional result, and a vet weighing surgical risk benefits from having both pieces of information rather than assuming one predicts the other perfectly.

For breeding purposes, the DNA result is what matters most, because it is what determines what a dog can pass on regardless of how that dog's own clotting happens to be performing today. A carrier-to-carrier pairing carries the same one-in-four statistical chance of producing a genetically affected puppy whether or not either parent has ever shown a clinical sign, which is the entire reason DNA panel testing exists as a breeding tool distinct from simply watching for bleeding problems in the parents themselves.

The practical guidance for a Sheltie owner holding a Type 1 panel result is this: a clear result closes the question. A carrier result means no personal clinical concern in the overwhelming majority of cases, but real relevance if that dog is ever bred. An affected result means clinical severity could range from nothing noticeable to a mild bleeding tendency, and the only way to know which applies to your specific dog is a functional blood test, ideally arranged well before any elective surgery is scheduled rather than as a same-day pre-operative scramble.