While studying a naturally-occurring polymorphism in the Hsp20 gene (S10F), we recently discovered that this mutation not only diminished the cardioprotective effects of Hsp20 in a transgenic mouse model, but mutant female mice also developed DCM during the course of 2 to 4 pregnancies that resulted in the death of 70% after three pregnancies and 100% after the fourth [14]. This evidence concerns the gene HSPB6 and familial dilated cardiomyopathy.