Genetic basis of Disproportionate dwarfism in Vizslas - is caused by a missense variant in the PCYT1A gene (c.673T>C), which changes an amino acid in the protein (p.Y225H). The PCYT1A gene encodes an enzyme involved in phospholipid biosynthesis, essential for normal skeletal development. This condition is inherited in an autosomal recessive manner, meaning that a dog must inherit two copies of the mutant gene (one from each parent) to express the disproportionate dwarfism phenotype.
Pathophysiology - The phenotype involves marked shortening and deformation of the long bones (especially humerus and femur), resulting in limbs that are disproportionately short compared to the body and head. The wrist (carpus) may appear thickened or knobby, particularly in puppies and young dogs. Affected Vizslas are generally healthy otherwise and can live normal lifespans, though some may develop orthopedic complications like hip dysplasia or osteoarthritis later in life.
Complications - Disproportionate limb shortening can lead to mobility challenges and predispose to joint issues like osteoarthritis and hip dysplasia. Despite skeletal abnormalities, affected dogs generally have good health and normal life expectancy.
Why This Matters to Breeders and Vets - This specific form of dwarfism had been untestable for many years but now has an available DNA test to identify carriers and affected animals. The mutation appears widespread in various Vizsla pedigrees, including show, field, and backyard lines. Early identification can prevent unintentional breeding of affected puppies and help maintain breed health.