Neurological and extra-neurological clinical spectrum observed in pediatric patients with EMC1 gene variants identified by whole exome sequencing

Background: The endoplasmic reticulum membrane protein complex 1 (EMC1) gene encodes a subunit of the EMC with multiple alternatively spliced transcripts encoding different isoforms. Monoallelic and biallelic mutations of the EMC1 gene have been reported for cerebellar atrophy, visual impairment, psychomotor retardation, lipoid proteinosis of Urbach and Wiethe, and Alkuraya-Kucinskas syndrome. Objectives: Herein, we present whole exome sequencing results of eight Saudi pediatric patients with distinctive clinical features which revealed both monoallelic and biallelic variants in the EMC1 gene (CHR1 exon4:19568918, NM_001271429.2, c.364G>A; p.A122T), including two previously reported siblings (CHR1 exon21:19547328, NM_015047.3, c.2602G>A; p.G868R). Results: The patients presented with the neurological and extra-neurological clinical spectrum that included seizures, spastic diplegia, cognitive impairment, axial and appendicular hypotonia, dysmorphic features, joint hyper-flexibility, attention deficit hyperactivity disorder, skeletal dysplasia in addition to generalized global developmental delay, failure to thrive, speech delay, intellectual disability, and visual impairments. Furthermore, brain Magnetic resonance imaging findings were consistent with variable clinical features and revealed brain atrophy, thinning of corpus callosum, semi-lobar holoprosencephaly, white matter abnormality, diffuse paucity of the myelin within the brain parenchyma, and reduction of white matter arborization in the temporal lobes. Conclusion: In conclusion, these clinical cases highlight the importance of the EMC1 gene in disease phenotype and add up to the expanded EMC1-related phenotype.