This 2014 La Jolla rodent study showed that treating the symptoms of an inherited disease can, through epigenetic DNA methylation, positively treat the symptoms in the subjects’ offspring.

The disease studied was Huntington’s, which is the most common inherited neurodegenerative disease:

• The treatment induced epigenetic changes in the expression of genes on the male Y chromosome.
• The treated male subjects were bred, and their sperm carried both the Huntington’s disease and the epigenetic changes that reduced the symptoms.
• The male offspring showed both delayed onsets of Huntington’s disease and reductions of specific symptoms when compared with both the treated subjects’ female offspring and the control group non-treated subjects’ male offspring.

http://www.pnas.org/content/112/1/E56.full “HDAC inhibition imparts beneficial transgenerational effects in Huntington’s disease mice via altered DNA and histone methylation”