Delineating the epilepsy phenotype of NRROS-related microgliopathy: A case report and literature review

Background: Negative regulator of reactive oxygen species (NRROS) related microgliopathy, a rare and recently recognized neurodegenerative condition, is caused by pathogenic variants in the NRROS gene, which plays a major role in the regulation of transforming growth factor-beta 1. Methods: We report a child presenting with infantile spasms syndrome (ISS) with subsequent progressive neurodegeneration who was identified to harbour a novel likely pathogenic NRROS variant (c.1359del; p.Ser454Alafs*11). The previously published reports of patients with this disorder were also reviewed systematically. Results: Including our index patient, 11 children (6 girls) were identified in total. Early development was normal in seven of these eleven children. All had a history of drug-resistant epilepsy, with 3 having epileptic spasms. The median age at seizure onset and developmental regression was 12 months, and the median age at death was 36 months. Intracranial calcifications were described in eight of eleven children. Neuroimaging revealed progressive cerebral atrophy and white matter loss in all children. The most common reported genetic variation was c.1981delC; (p.Leu661Serfs*97) observed in two families (likely due to a founder effect). Conclusions: Pathogenic variants in NRROS should be suspected in children with neuro-regression and drug resistant epilepsy including ISS with onset in the first two years of life. Punctate or serpiginous calcifications at the grey-white matter junction and acquired microcephaly are further clues towards the diagnosis.

Automated summary

Pathogenic variants in the NRROS gene are associated with infantile spasms syndrome and progressive neurodegeneration. Among the 11 identified children, 7 had normal early development. All children had a history of drug-resistant epilepsy, with 3 experiencing epileptic spasms. The median age at seizure onset and developmental regression was 12 months and the median age at death was 36 months. Eight of the children had intracranial calcifications and neuroimaging showed progressive cerebral atrophy and white matter loss.