J Genet Med.  2019 Dec;16(2):55-61. 10.5734/JGM.2019.16.2.55.

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

Affiliations
  • 1Department of Pediatrics, Gachon University Gil Medical Center, Gachon University College of Medicine, Incheon, Korea.
  • 2Department of Laboratory Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
  • 3Department of Pediatrics, Pediatric Clinical Neuroscience Center, Seoul National University Children's Hospital, Seoul National University College of Medicine, Seoul, Korea. chaeped1@snu.ac.kr
  • 4Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea.

Abstract

PURPOSE
Genetic defects in the nuclear-encoded mitochondrial aminoacyl-tRNA synthetases were first identified as causes of various disorders in 2007. Variants in IARS2, which encodes a mitochondrial isoleucyl-tRNA synthetase, were first reported in 2014. These variants are associated with diverse phenotypes ranging from CAGSSS (CAtaracts, Growth hormone deficiency, 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 identified five 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 findings 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 first report of Korean patients with IARS2-related disorders. Our findings broaden the phenotypic and genotypic spectrum of IARS2-related disorders in Korea and will help to increase clinical awareness of IARS2-related neurodegenerative diseases.

Keyword

Amino acyl-tRNA synthetases; Cataract; IARS2; Leigh disease
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