<h4>Background</h4>X-linked dystonia-parkinsonism (XDP), an adult-onset neurodegenerative disorder, is caused by an SVA insertion in the <i>TAF1</i> gene, containing a hexanucleotide, the length of which is correlated to the severity of the disease. The gene discussed is TAF1; the disease is X-linked dystonia-parkinsonism.