• homozygosity;
  • Machado–Joseph disease;
  • rapid eye movement (REM) sleep behaviour disorder

A male patient carrying the homozygous gene for Machado–Joseph disease (MJD) presented at age 43 with sleep disturbances and psychiatric symptoms followed by ataxic speech and gait. A polysomnogram (PSG) showed decreased rates of sleep time and stage rapid eye movement (REM) and an increased rate of ‘stage 1-REM with tonic EMG’ (Tachibana et al., 1975); all compatible with REM sleep behaviour disorder (RBD). Molecular gene analysis at age 59 showed that the CAG repeat units in the MJD gene were 60 and 60, smaller than the reported lengths for homozygous MJD patients (63–70 and 66–72). In addition to sleep disturbances, in particular RBD, psychiatric symptoms may be important clinical features in both heterozygous and homozygous MJD.