Unusual occurrence of temporo-spatial cluster of human prion disease in northern part of central Slovakia

OBJECTIVES: Clusters of human prion diseases have been reported in several endemic regions, notably in Slovakia, Italy, Chile, and Israel, predominantly linked to genetic forms (E200K mutation). Isolated temporo-spatial clusters that include sporadic forms are rarely documented and remain poorly understood. This report describes a unique cluster of prionopathies observed in northern central Slovakia. METHODS: Between July 2021 and March 2022, three definitive cases of prion disease were identified in two neighbouring rural villages, Pribovce and Rakovo, in the Martin District of Slovakia. The villages, located within a radius of approximately three kilometres, have a combined population of 1,468. Clinical records, epidemiological data, and neuropathological findings were reviewed in all cases. RESULTS: The cluster included one genetic Creutzfeldt-Jakob disease (gCJD) with the PRNP E200K mutation and M/M genotype at codon 129; one sporadic CJD (sCJD); and one sporadic fatal familial insomnia (sFFI), the first such case reported in Slovakia. The cases occurred sequentially within a ten-month interval. No familial, environmental, or iatrogenic links were identified. CONCLUSIONS: The coexistence of distinct prionopathies in such a confined population and period is exceptional. Despite comprehensive investigation, no explanatory factor was found, and this cluster likely represents a chance occurrence of epidemiological interest. The finding underscores the importance of systematic neuropathological confirmation, molecular testing, and regional surveillance in prion disease monitoring.