ATXN2 and essential thrombocythemia: For instance, both ATXN1 and ATXN2 intermediate expansions are associated with an increased risk of developing amyotrophic lateral sclerosis.32  HTT intermediate expansions give rise to the risk of multisystem atrophy,33 and could confer late-onset abnormal motor and cognitive phenotype.34 Our results suggest that intermediate and pathogenic repeat expansions of these tremor-associated STRs did not increase the risk of familial ET or influence phenotypes of ET patients.