It has a silky, smooth coat and commonly a smooth undocked tail. The breed standard recognizes four colors: Blenheim (chestnut and white), Tricolor (black/white/tan), Black and Tan, and Ruby. The breed is generally friendly, affectionate and good with both children and other animals; however, they require much human interaction. Some serious genetic health problems, including early-onset mitral valve disease (MVD), the potentially severely painful syringomyelia (SM), hip dysplasia, luxating patellas, and certain vision and hearing disorders are health problems for this breed. As today's Cavaliers all descend from only six dogs, any inheritable disease present in at least one of the original founding dogs can be passed on to a significant proportion of future generations. This is known as the founder effect and is the likely cause of the prevalence of MVD in the breed.