AGK and Congenital cataract - hypertrophic cardiomyopathy - mitochondrial myopathy: To date, only three studies have investigated families with Sengers syndrome and identified different types of loss-of-function mutations in AGK gene, including start codon mutations (compound heterozygous), nonsense (compound heterozygous), frameshift (compound heterozygous) and splice site mutations (homozygous and compound heterozygous) [4,16].