TFDP1 and Dystonia: Epistasis and epigenetics (DNA methylation or histone deacetylation) are additional mechanistic considerations [51] that could explain why the father and brother are asymptomatic carriers of the structural variant while the proband manifests dystonia due to overexpression of TFDP1. Conversely, TFDP1 may have played no causal role in our patient’s dystonia and other clinical manifestations.