Janus Parasiticus

JANUS PARASITICUS (Janus - a Roman deity depicted with two faces), a double symmetrical malformation consisting of the fusion of two normally developed fetuses in the area of the face and head (usually also in the area of the neck and chest); hence the synonym cephalothoracopagus. Depending on whether the sagittal planes of both fetuses are common or cross at an angle, as well as on the completeness of the fusion of parts of the skull and face in terms of the common size and appearance of the head, face, ears, eyes, mouth, etc. (combinations with aprosopia, cyclopia, microstomia, astomia, synotia), the external appearance of J. will vary. In cases where the fusion also includes one pair of arms, it is referred to as deradelphus. The upper part of the digestive tract (esophagus, stomach, duodenum and intestines) up to the point of departure of the ductus omphalo-entericus is single, after which the intestines are separate; usually two hearts are observed, not always properly developed; the navel is common. J. p. belongs to the number of rare malformations.