The clinical features of familial focal epilepsy with variable foci and NPRL3 gene variant

by Yue Wang, Peimin Yu, Guoxing Zhu, Xunyi Wu, Ding Ding, Zhen Hong

Familial focal epilepsy with variable foci (FFEVF) is a rare type of focal epilepsy syndrome; it is associated with NPRL3 variant. However, relevant reports are rare in China. We aimed to analyze the clinical features of Chinese patients with FFEVF to understand further the differences between various NPRL3 variants and explored the effect of NPRL3 variant on mRNA.

We ran a full workup on a family with FFEVF (four patients, one healthy member): an inquiry of medical history, cranial magnetic resonance imaging (MRI), electroencephalogram (EEG), and whole exon sequencing. Their clinical features were compared with those of other FFEVF patients in published reports. The mRNA splicing changes were analyzed quantitatively and qualitatively using real-time quantitative—polymerase chain reaction (q-PCR) and reverse transcription (RT)-PCR and compared between our patients and healthy individuals.

Patients with NPRL3: c.1137dupT variant had a wide range of onset age (4 months to 31 years), diverse seizure types, variable foci (frontal lobe/temporal lobe), different seizure times (day/night) and frequencies (monthly/seldom/every day), different therapeutic effects (refractory epilepsy/almost seizure free), normal MRI, and abnormal EEG (epileptiform discharge, slow wave). The phenotypic spectrum with different NPRL3 variants was either similar or different. Significantly different relative quantities of mRNA were found between patients and healthy individuals in real-time qPCR. Abnormal splicing was observed in patients compared with healthy individual in RT-PCR. Despite having the same gene variant, different family members had different mRNA splicing, possibly causing different phenotypes.

The clinical features of FFEVF varied, and auxiliary inspection was atypical. NPRL3: c.1137dupT could change the relative quantity of mRNA and cause abnormal splicing, which might produce different phenotypes in different family members.