Bladder exstrophy and epispadias complex (BEEC) is an anterior midline defect with variable expression involving the infraumbilical abdominal wall including the pelvis, urinary tract, and external genitalia (Gearhart and Jeffs, 1998). BEEC is one of the most severe urologic birth defects because of its profound impact on continence, sexual function, and morbidity due to the effect of chronic and recurrent infections on renal function. The term 'exstrophy,' derived from the Greek work ekstriphein, which literally means 'turn inside out,' was first used by Chaussier in 1780. Martinez-Frias et al. (2001) emphasized that exstrophy of the cloaca and exstrophy of the bladder are 2 different expressions of a primary developmental field defect. Cloacal exstrophy is a feature of the OEIS (omphalocele-exstrophy-imperforate anus-spinal defects) complex (258040). Exstrophy of the cloaca includes the persistence and exstrophy of a common cloaca that receives ureters, ileum, and a rudimentary hindgut and is associated with failure of fusion of the genital tubercles and pubic rami, incomplete development of the lumbosacral vertebrae with spinal dysraphism, imperforate anus, cryptorchidism and epispadias in males and anomalies of the mullerian duct derivatives in females, and a wide range of urinary tract anomalies. Omphalocele is common, and most patients have a single umbilical artery. Reutter et al. (2016) reviewed the epidemiology, potential mechanisms, and animal models for BEEC. They described BEEC as a spectrum of component malformations of variable severity, including epispadias as the mildest phenotype and classic bladder exstrophy as the most common, with cloacal exstrophy representing the most severe form. In approximately one-third of cases, urologic malformations are present, including ectopic kidney, renal agenesis, and/or hydronephrosis. Other malformations involving the gastrointestinal, skeletal, spinal, and genitourinary systems, including cryptorchidism and ambiguous genitalia, are reported frequently. The authors noted that cloacal exstrophy is considered by some to have a different embryologic origin from classic bladder exstrophy. [from OMIM]