There is convincing evidence that germline NKX2-5 mutations are aetiologic in CHD.5–7 The aim of our current study was to replicate the previous finding of somatically derived sequence variants in patients with septal defects.10, 13 In these published reports, somatic NKX2-5 sequence variants were primarily identified within malformed regions and were not seen in unaffected regions of the heart; taken together, these findings suggest that somatic mutations occur with high frequency and are also aetiologic in CHD.10, 13. This evidence concerns the gene NKX2-5 and Abnormal cardiac septum morphology.