Congenital and Breed-Associated Vertebral Anomalies in Dogs and Cats: Developmental Anatomy, Genetic Determinants, and Biological Significance.

Congenital and breed-associated vertebral anomalies in dogs and cats encompass a heterogeneous group of abnormalities affecting vertebral formation, segmentation, regional identity, and number. Their interpretation requires integration of postnatal anatomy with developmental biology and genetic evidence, because similar morphological phenotypes may arise through different mechanisms and breed association does not necessarily imply a shared genetic cause. This structured narrative review synthesizes current knowledge on developmental anatomy, regional vertebral morphology, congenital and transitional anomalies, breed-associated phenotypes, and established genotype-phenotype relationships in dogs and cats. Particular attention is given to the distinction between morphological description and demonstrated developmental or molecular causation. Evidence involving DVL2 in screw-tailed brachycephalic dogs and TBXT in naturally short-tailed dogs and Manx cats illustrates both the value and the limitations of single-gene explanations, including variable expressivity, allelic heterogeneity, and population specificity. Precise anatomical phenotyping emerges as a prerequisite for meaningful genetic analysis and breeding-oriented interpretation. Future progress will depend on standardized phenotype definitions, better-characterized populations, species-specific genetic studies, and functional validation of candidate mechanisms. Integrating developmental anatomy and genetics provides a rigorous framework for understanding the biological significance of congenital vertebral diversity in dogs and cats.