FXN and Friedreich ataxia: Where full sequencing of FXN GAA repeats has been possible due to comparatively short repeats (up to approximately 130 repeats), there are reports of interrupted GAA repeat expansion sequences, such as (GAGGAA)5-9 or (GAAGGA)65, and these are associated with either absence of FRDA disease phenotype (Cossee et al., 1997; Montermini et al., 1997; Ohshima et al., 1999) or atypical mild late-onset or very late-onset FRDA disease phenotype (Cossee et al., 1997; Epplen et al., 1997; Moseley et al., 1998; McDaniel et al., 2001; Sharma et al., 2004; Stolle et al., 2008).