FGF14 and bile duct papillary neoplasm: Shorter GAA expansions at the FGF14 locus (~250 repeats) are reported to be associated with reduced penetrance and variable meiotic stability in late-onset ataxia, which likely hampered the initial identification of the disease.63 64 The discovery of additional pathogenic STR expansions for IPN may be similarly masked by phenotypic and genetic factors.