Dipygus is a severe

congenital deformity A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can r ...

where the body axis forks left and right partway along the

torso The torso or trunk is an anatomical term for the central part, or the core, of the body of many animals (including humans), from which the head, neck, limbs, tail and other appendages extend. The tetrapod torso — including that of a huma ...

with the posterior end ( pelvis and legs) duplicated. Myrtle Corbin was a dipygus; she married and had five 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 Francesco "Frank" Lentini (May 18, 1889 − September 21, 1966) was an Italian-American sideshow performer who toured with numerous circuses. Born with a parasitic twin, Lentini had three legs. Early life Lentini was born at 8 Gintoli Street, Ros ...

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 Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in dysmorphology. The related t ...

factors. It occurs early in intrauterine life.

References

Congenital disorders Rare diseases Parasitic twin {{Congenital-malformation-stub