PDGFB and Cognitive impairment: Later, Ramos and coll [70], by screening the well-known PFBC genes in four cohorts from America and Europe, found known and novel mutations of SLC20A2, PDGFB, PDGFRB, and XPR1, confirming the higher prevalence of SLC20A2 as the major causative gene (up to 13%) and, consistent with previous series, the most frequent symptoms were parkinsonism (52.3% of symptomatic individuals), cognitive impairment (40.9%), and psychiatric signs (38.6%) [70].