RARS2 mutations cause early onset epileptic encephalopathy without ponto-cerebellar hypoplasia

Early onset epileptic encephalopathies (EOEEs) are a group of devastating diseases, manifesting in the first year of life with frequent seizures and/or prominent interictal epileptiform discharges on the electroencephalogram, developmental delay or regression and usually a poor prognosis. There are numerous causes for EOEEs making the diagnostic workup time consuming and costly.

We describe two siblings with fatal EOEE, profound global developmental delay and post-natal microcephaly that underwent extensive biochemical and metabolic workup in vain. Neuro-imaging disclosed non-specific progressive cerebral atrophy.

Whole-exome sequencing (WES) disclosed compound heterozygous mutations in the gene encoding for mitochondrial arginyl-transfer RNA synthetase, RARS2. This gene has been previously described as the cause of pontocerebellar hypoplasia type 6.

We suggest that RARS2 gene mutations can cause a metabolic neurodegenerative disease manifesting primarily as EOEE with post-natal microcephaly, without the distinctive radiological features of pontocerebellar hypoplasia.