MT-TK and night blindness: More specifically, pathogenic mutations in the MTTK gene predominantly result in multisystemic disorders that affect the central nervous system including the MERRF syndrome.7 Jeppesen and colleagues recently described a patient with a heteroplasmic m.8340G>A MTTK variant manifesting as isolated myopathy.8 Here, we report a case of a 39-year-old man harbouring the identical mtDNA point mutation with an extended phenotype of childhood epilepsy, migraines and sensorineural deafness who presented to eye clinic with night blindness and cataracts.