PRNP and prion disease: On the other hand, data from inherited prion disease demonstrated positive RT-QuIC seeding activity in 1/10 asymptomatic carriers of the E200K PRNP mutation (which causes a rapid CJD-type phenotype), implying that seeding activity is not consistently present for long periods prior to symptom onset in E200K carriers, although the one seeding positive individual, who was near the median age of onset, remained asymptomatic 1 year later (Vallabh et al., 2020).