Dipygus

Myrtle Corbin, a famous dipygus.

Piglet with dipygus at Ukrainian National Chernobyl Museum in Kiev

The dipygus deformity is a severe congenital deformity where the body axis forks left and right partway along the torso with the posterior end (pelvis and legs) duplicated. Myrtle Corbin was a dipygus; she married and had 5 children. In human cases the inner two of the four hindquarters develop much smaller than normal. This is a type of "teras catadidymum" ("monster twinned below").

Another sort of deformity with extra legs can happen from a degenerated conjoined twin, as may have happened with Frank Lentini with his third leg.

Signs

Dipygus manifests as duplicated lower limbs, and could include additional organs or bodily structures.

Causes

Dipygus is caused by genetic, environmental, or teratogenic factors. It occurs early in intrauterine life.