The mutated alleles identified in our Japanese patients with OPMD were most likely due to duplications of (GCG)(3)GCA and (GCG)(2)(GCA)(3) but not simple expansions of the GCG repeats. Therefore, unequal crossing-over of 2 PABP2 alleles, rather than DNA slippage, is probably the causative mechanism of OPMD mutations. All mutations that have been reported in patients with OPMD so far can be explained with the mechanism of unequal crossing-over. On the other hand, comparison of the clinical features of our patients with those of other patients in previous reports suggests that specific clinical features cannot be attributed to the length of the polyalanine tract per se.

REM sleep without atonia, first described in experimental cats with bilateral lesions in the dorsolateral pontine tegmentum, 1 was found to be associated with behavioural manifestations, ranging from REM sleep without atonia associated with no behavioural correlates to that with active locomotor disinhibition, depending on the location and size of the lesions.2 Experimental cats with active locomotion along with violent behaviours have been considered an animal model for REM sleep behaviour disorder seen in neurological diseases with brainstem lesions.3-5 Based on these experimental findings, we hypothesised that REM sleep motor dysfunction might occur even in patients with multiple system atrophy who do not report any nocturnal abnormal behaviours. Furthermore, by utilising all night polysomnography, the only method capable of detecting this kind of REM sleep abnormality that does not fulfill the criteria of REM sleep behaviour disorder, we aimed at elucidating how sleep related clinical symptoms are related to REM sleep motor dysfunction in patients with multiple system atrophy. Patients and methods PATIENTS

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Reducing body myopathy is a rare muscle disease defined by abnormal inclusions in affected muscle fibers that can be stained with menadione-nitroblue tetrazolium. The origin of these inclusions has not been determined. Here we show that reducing bodies bear characteristics of nucleoli. Ultrastructurally, muscle biopsy specimens of a patient with adult-onset reducing body myopathy showed granular structures of reducing bodies with features similar to the granules of nucleoli, which consisted of pre-ribosomes. In addition, reducing bodies were positive for histochemistry of argyrophilic nucleolar organizer regions (a method for detecting the areas where ribosomal RNA is actively transcribed in the nucleolus), and for antibodies against nucleoli and nuclear ribonucleoprotein. The current findings suggest that reducing bodies contain pre-ribosomes and their associated proteins of the nucleolus and that formation of reducing bodies may result from defects of processing and assembly of ribosomes.