AGK and Congenital cataract - hypertrophic cardiomyopathy - mitochondrial myopathy: Genetic testing of a boy revealed a homozygous pathogenic variant for Sengers syndrome in <i>AGK</i> (c.1131+2T>C) which was classified as likely pathogenic according to the ACMG guideline; besides, his skeletal muscle biopsy and transmission electron microscope presented obvious abnormity.