A case of epigastric heteropagus twinning with other congenital abnormalities in a Chihuahua puppy

A two-year-old Chihuahua was presented on day 58 of pregnancy due to very marked abdominal distension. A cesarean section was performed and five normal and one clearly abnormal puppy were delivered. Examination of the abnormal puppy revealed a combination of congenital anomalies including epigastric heteropagus twinning. The autosite showed focal cranial aplasia cutis, anasarca, lissencephaly, palatoschisis, sternal agenesis and eventeratio (gastroschisis/schistocoelia). The partly formed parasitic twin was attached at the sternal region of the autosite and demonstrated four formed limbs, atresia rectum, atresia ani, a single kidney, tail agenesis and atresia vulvae. To the authors' knowledge, this is only the third reported case of heteropagus conjoined twinning in the dog and the first reported case of canine epigastric heteropagus twinning. In addition, there appear to be no reports in the veterinary literature noting an association with conjoined twinning in the dog with focal cranial aplasia cutis, eventeratio, lissencephaly, palatoschisis and anasarca. An in-depth literature review was hampered by the lack of a uniform nomenclature to identify this type of conjoined twinning.