PCNA and Cockayne syndrome: For instance, epileptic encephalopathy, childhood-onset (EEOC) and ataxia-telangiectasia like disorder 2 (ATLD2) clustered with Cockayne syndrome and XPA, Warsaw breakage syndrome (WABS) clustered with Seckel and Nijmegen breakage syndrome and Meier-Gorlin syndrome (MGORS) clustered with acromicric dysplasia.