Specifically, prominent square-wave jerks were identified in FRDA and SCA1, downbeat nystagmus was frequently reported in SCA6, EA2, A-T, SCA27B and RFC1-related ataxia, whereas gaze-evoked nystagmus was observed in SCA1, SCA3, SCA6, EA2, AOA1 and AOA2. The gene discussed is FXN; the disease is pathologic nystagmus.