Von Willebrand's Disease Type 1 in Welsh Springer Spaniels: Why Severity Varies So Much

Type 1 von Willebrand's disease involves a partial reduction in the clotting protein rather than the near-complete absence seen in the rarer, more severe Type 2 and Type 3 forms. This makes Type 1 generally less dangerous on average, but 'partial reduction' covers a genuinely wide range, some affected dogs have levels only slightly below normal and show essentially no clinical signs ever, while others have levels low enough to cause real bleeding risk during surgery or significant trauma.

This variability is part of why a genetic test confirming Type 1 status doesn't fully answer the practical question of how much bleeding risk a specific dog actually carries; the genetic result tells you the type, but an actual von Willebrand factor blood level test tells you the degree, and both pieces of information matter for real surgical planning. A dog testing genetically positive for Type 1 with a factor level close to normal carries meaningfully less risk than one with a factor level substantially reduced, even though both would be labeled the same genetic type.

For breeding purposes, Type 1 is generally considered manageable within a breeding program with appropriate testing and informed pairing decisions, unlike the more severe forms where breeding recommendations are typically much stricter. This distinction is exactly why knowing the specific type, not just a general von Willebrand's disease diagnosis, changes both an individual dog's surgical planning and a breeder's approach to future litters.

Because Type 1 covers such a wide severity range, getting the most useful information out of a diagnosis means pairing the genetic type with an actual factor level measurement.