EXOSC9 and Cerebellar atrophy: These EXOSC9-related phenotypes closely resemble the clinical spectrum of other exosomal defects, which could be referred to as “exosomopathies.” The clinically unique combination of a motor neuronopathy with cerebellar atrophy typical for the exosomopathies link the other two major clinical groups of the disorders of RNA processing, namely SMA without cerebellar involvement on the one end and the pontocerebellar hypoplasias without SMA on the other.