Clinical and genetic characteristics of Korean patients with IARS2-related disorders

Abstract

Purpose: Genetic defects in the nuclear-encoded mitochondrial aminoacyl-tRNA synthetases were ἀrst identiἀed as causes of various disorders in 2007. Variants in IARS2, which encodes a mitochondrial isoleucyl-tRNA synthetase, were ἀrst reported in 2014. These variants are associated with diverse phenotypes ranging from CAGSSS (CAtaracts, Growth hormone defi-ciency, Sensory neuropathy, Sensorineural hearing loss, and Skeletal dysplasia) and Leigh syndrome to isolated nonsyndromic cataracts. Here, we describe the phenotypic and genetic spectrum of Korean patients with IARS2-related disorders. Materials and Methods: Using whole-exome sequencing followed by Sanger sequencing, we identiἀed ἀve patients with IARS2 mutations. Their medical records and brain magnetic resonance images were reviewed retrospectively.Results: All five patients presented with developmental delay or regression before 18 months of age. Three patients had bilateral cataracts, but none had hearing loss or sensory neuropathy. No evidence of skeletal dysplasia was noted, but two had short stature. One patient had cardiomyopathy and another exhibited renal tubulopathy and hypoparathyroidism. Their brain imaging ἀndings were consistent with Leigh syndrome. Interestingly, we found the recurrent mutations p.R817H and p.V105Dfs*7 in IARS2. Conclusion: To our knowledge, this is the ἀrst report of Korean patients with IARS2-related disorders. Our ἀndings broaden the phenotypic and genotypic spectrum of IARS2-related disorders in Korea and will help to increase clinical awareness of IARS2-related neurodegenerative diseases.