NUTM2B and fragile X-associated tremor/ataxia syndrome: Recently, noncoding GGC repeat expansions in NOTCH2NLC, FMR1, NUTM2B‐AS1 have been identified as the causative dynamic mutations based on the long read sequencing technology for three types of adult leukoencephalopathies: neuronal intranuclear inclusion disease (NIID), fragile X tremor/ataxia syndrome (FXTAS) and oculopharyngeal myopathy with leukoencephalopathy (OPML), respectively.7