Gerstmann–Sträussler–Scheinker syndrome (GSS) is a very rare, usually familial, fatal neurodegenerative
disease that affects patients from 20 to 60 years in age. This extremely rare disease is classified as a
transmissible spongiform encephalopathy (TSE). The exact
incidence of GSS is unknown but is estimated to be between 1 and 10 per 100 million.