MRPS22 gene defect is a very rare newly discovered mitochondrial disorder. We report a 4-month-old severely affected male infant with MRPS22 mutation. Whole exome sequencing revealed a novel homozygous splicing mutation c.339 + 5 G > A in MRPS22 gene. He has mild dysmorphism, hypotonia, developmental delay but not hypertrophic cardiomyopathy and tubulopathy which differ from other majority of reported patients. Therefore, hypertrophic cardiomyopathy and tubulopathy may not be considered as constant features of MRPS22. With this case report, we also present first symmetrical bilateral brainstem and medial thalamic lesions, and cerebellar and cerebral atrophy on a brain MR imaging follow-up of ten months.
Keywords: Developmental delay; Hypotonia; Leigh syndrome; MRPS22; Mitochondrial disorder; Mosaic down syndrome.