ERCC6 and microcephaly: <h4>Background</h4> Cockayne syndrome is an ultra-rare (1:2.5 million) hereditary disease from the group of progeroid syndromes caused by pathogenic and probable-pathogenic variants in DNA repair genes (ERCC8, ERCC6, XPB (ERCC3), XPD (ERCC2) and XPG (ERCC5)) and characterized by abnormal photosensitivity, congenital cataract, microcephaly, sensorineural hearing loss, nervous system pathology and other multisystem changes.