Diphallia

Diphallia, also called penile duplication, is an extremely rare developmental abnormality in which a male is born with two penises, occurring in about 1 in 5.5 million newborns. The first reported case was by Johannes Jacob Wecker in Bologna in 1609, and roughly one hundred cases have been reported since. It is usually accompanied by renal, vertebral, hindgut, anorectal or other congenital anomalies, and carries a higher risk of spina bifida, so affected infants face higher mortality from infections linked to more complex renal or colorectal systems. It is thought to arise between the 23rd and 25th days of gestation when injury, chemical stress or malfunctioning homeobox genes disturb the caudal cell mass. Classifications by Schneider in 1928 and Aleem in 1972 separate true diphallia from a bifid phallus, each either partial or complete.