Neurodegeneration, Intracranial Calcifications, Microcephaly and Drug-Resistant Epilepsy Caused by a Novel Homozygous Missense Variant in the NRROS Gene: A Case Report

Mohammed A Al-Omari Department of Pediatrics, College of Medicine, Imam Abdulrahman bin Faisal University, Dammam, King Fahad Hospital of the University, Al-Khobar, Saudi ArabiaCorrespondence: Mohammed A Al-Omari, Department of Pediatrics, College of Medicine, Imam Abdulrahman bin Faisal University, Dammam, King Fahad Hospital of the University, P.O. Box 2208, Al-Khobar, 31952, Saudi Arabia, Tel +966-13-896.6666 (Ext.1639), Fax +966-13-896.6770, Email [email protected]: Negative regulator of reactive oxygen species (NRROS)-related microgliopathy (MIM# 618875) is a rare autosomal recessive neurodegenerative disorder. This case report describes a Saudi Arabian child with a novel homozygous NRROS variant, NM_198565.2: c.257T>C (p.Leu86Pro) presenting with drug-resistant epilepsy, rapid developmental regression, microcephaly, dystonia, and intracranial calcifications. Neuroimaging revealed bilateral intracranial calcifications, generalized brain volume loss, and connatal cysts; EEG showed a slow, suppressed background with multifocal epileptiform discharges. The variant is predicted to be deleterious by multiple in silico tools, suggesting a pathogenic effect on microglial function. This case underscores the importance of considering NRROS-related microgliopathy in children with early-onset neurodegeneration, drug-resistant epilepsy, and intracranial calcifications, enabling targeted genetic testing, diagnosis, and counseling.Keywords: NRROS gene, microgliopathy, intracranial calcification