[Terata catydidymus dicephalus: description of a case].

Conjoined twinning is the result of an abnormal developmental process of "twinning" in which two similar weighted and sized twins are partially conjoined and show a total symmetry independently from the pattern of conjunction. They are classified in three groups: Terata Catydidymus, Terata Anadidyma and Terata Anacatadidyma. Among Terata Catydidymus the dicephalus subtype is a rare abnormality with a severe prognosis compared to other subtypes as: diprosopus, pyophagus and ischiopagus. We report the case of a fetus at the 15th weeks of pregnancy. The external examination revealed severe diffuse somatic malformations consisting of dicephalia with a double neck in conjunction to a single chest, a single abdomen, a double spine conjoined distally near the sacrum, buds of ribs in between the two spines with mid clavicular and scapular fusion following the major axis of the two bones. Arms and legs revealed no abnormalities. Central nervous system structures were normally developed and the two hemispheres seemed completely separated and independent one to the other. We believe that the case described is interesting being Terata Catydidymus a rare phenomenon, being the dicephalus subtype still lesser frequent and its occurrence in males quite exceptional.