CGG Repeat Expansion in NOTCH2NLC Causing Overlapping Oculopharyngodistal Myopathy and Neuronal Intranuclear...

CGG repeat expansion in the 5' untranslated region (5'UTR) of the Notch 2 N-terminal-like C gene (NOTCH2NLC) has been associated with neuronal intranuclear inclusion disease (NIID) and oculopharyngodistal myopathy type 3 (OPDM3). Few OPDM3 patients have been reported. This report describes two OPDM3 patients with novel imaging findings who presented the typical features of NIID, and reviews all OPDM3 cases available in the literature.

The available clinical, imaging, and pathological information was reviewed and investigated. CGG repeat expansion in the 5'UTR of NOTCH2NLC was tested using the repeat-primed polymerase chain reaction (PCR), followed by the fluorescence amplicon-length PCR to determine the number of CGG repeats.

Our two OPDM3 patients and most patients reported in the literature developed the typical clinical characteristics of NIID, including leukoencephalopathy, peripheral neuropathy, cognitive deterioration, pigmentary retinopathy, ataxia, tremor, acute encephalitis-like episodes, pigmentary retinopathy, miosis, and sensorineural hearing loss. In addition to typical imaging findings of NIID, our two patients exhibited diffusion weighted imaging (DWI) hyperintensities in the middle cerebellar peduncles, which have not been described previously. Muscle biopsies revealed rimmed vacuoles and p62-positive intranuclear inclusions in the myofibers in both patients. The skin biopsy performed in one patient detected typical eosinophilic intranuclear inclusions. Genetic analysis identified CGG repeat expansion in NOTCH2NLC as the causative mutation in the two patients.

Our two patients with OPDM3 had clinical characteristics of NIID and exhibited DWI abnormality in the cerebellum. Our results indicate that OPDM3 is within the spectrum of NIID and that DWI hyperintensities in the cerebellum are helpful for diagnosing NIID or OPDM3.