Caudal duplication anomaly is a rare type of developmental disorder that arises from incomplete separation of mono-ovular twins. It can involve various congenital anomalies, but the hallmark is duplication of organs in the caudal region, and most frequently affected organs are genitourinary and gastrointestinal tracts. Recently AXIN1 promotor has been shown to have methylation in patients with caudal duplication anomaly.
