The spectrum of clinical symptoms of PFBC is further complicated by the presence of known mutations in a second gene that may contribute to or be entirely responsible for the disease manifestation [73], such as SLC20A2 and the neighboring THAP1 gene in a large dystonia family [74] or changes in the epilepsy-linked SCN2A gene in combination with SLC20A2 variants in PFBC patients with refractory seizures [75]. This evidence concerns the gene THAP1 and bilateral striopallidodentate calcinosis.