DNA2 and congenital myopathy with cores: An example is DNA2, a multi‐catalytical (helicase/nuclease) protein found in mammalian mitochondria, where it participates in the removal of damaged bases in the Base Excision Repair (BER) pathway and the removal of RNA primers during mtDNA replication.3 We have previously identified DNA2 missense mutations in adult patients presenting with progressive myopathy and muscle mtDNA deletions (MIM 615156).4 Since then, DNA2 mutations have been detected in Seckel syndrome (MIM 615807)5 and congenital myopathy.6, 7