This is a complicated question. Cases of juvenile cardiomyopathy have been observed in English Toy Terriers, however all cases reported to this study have had pedigrees that include Toy Manchester Terriers. It is recommended that English Toy Terrier breeders with Toy Manchester Terrier behind their dog(s) test their breeding stock. It is also recommended that English Toy Terrier Clubs or individual breeders interested in determining whether the gene exists in the pure ETT population consider further investigation through testing.