According to Chouliaras et al. [32], patients with PSP have a high NFL but no significant increase in other biomarkers such as P-tau181, Aβ42/40, and GFAP (glial fibrillar acidic protein) [35], which was partially found in our case, as TAU and Aβ42/40 were decreased in the twin diagnosed with PSP. The gene discussed is NEFL; the disease is supranuclear palsy, progressive, 1.