Anat. Histol. Embryol. 36, 179–181 (2007) ISSN 0340–2096 doi: 10.1111/j.1439-0264.2006.00731.x Short Communication Faculty of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria A Case of Craniothoracopagus (Monocephalus Thoracopagus Tetrabrachius) in a Dog H. O. Nottidge, T. O. Omobowale*, J. O. Olopade, O. O. Oladiran and O. O. Ajala Address of authors: Faculty of Veterinary Medicine, University of Ibadan, Oyo State, Nigeria; *Corresponding author: Tel.: +234 805 614 373; fax: +234 2 810 3043; e-mail: bukitayo_omobowale@yahoo.com With 4 figures Received March 2006; accepted for publication April 2006 Summary Introduction This report describes a case of craniothoracopagus (moncephalus thoracopagus tetrabrachius) twin puppies in Ibadan, Nigeria. The conjoined twins were given birth to by a 7-yearold bitch that was usually allowed to stray away from home in search of food. Deformities of the cardiovascular, digestive musculoskeletal, respiratory and urinary systems are reported. This is probably the first report of craniothoracopagus twinning in a dog. Defects that are present at birth are known as congenital abnormalities and they arise from errors during development (Noden and de Lahunta, 1985). An example of such congenital abnormalities is conjoined twinning which is referred to in common parlance as Siamese twinning. Conjoined twins are the product of a single ovum and are monozygotic (Nichols, Fig. 1. Dorsal view showing the set of dorsally placed forelimbs, four hind limbs and two tails. Ó 2006 The Authors. Journal compilation Ó 2006 Blackwell Verlag Fig. 2. Ventral view of the craniothoracopagus twin. www.blackwell-synergy.com 180 1979). Classification is based on the nature and degree of union, e.g. thoracopagus, pygopagus and craniopagus (Sadler, 2000). A case of canine craniothoracopagus twinning is described in this article. Case History, Necropsy and Radiological Findings Newly whelped conjoined female twin puppies were delivered by a 7-year-old bitch without obstetrical assistance and were presented dead to the Veterinary Teaching Hospital of the University of Ibadan. The bitch, which was usually allowed to stray about in the neighbourhood in search of food, had had previous parturitions with normal puppies. The conjoined puppies were from the same litter of seven other puppies. The first two came out alive followed by the dead conjoined twins and serially by the others, which were dead in utero. On examination of the conjoined twins, there was brachygnatism and the head was a little larger than normal. The thorax and abdomen were more extensive than in normal puppies. There were two sets of forelimbs (making four in all). While a set of forelimbs was in normal spatial orientation, a second pair was dorsally placed (Figs 1 and 2). There were two distinct and separate pelvis, four hind limbs, two tails, two umbilici and partial joining of the abdomen (Fig. 2). Fig. 3. Radiograph showing two spines, two lateral condyles and a fused medial condyle. H. O. Nottidge et al. X-ray examination revealed two distinct spines resulting from two lateral and an apparently fused medial occipital condyle. The two atlas bones were partially related, medially with the fused medial occipital condyle and also to the lateral occipital condyle. All the other cervical bones, starting from the axis, were separate, distinct from each other and duplicated. In addition, the spinal column showed scoliosis (curvature of the spine) (Figs 3 and 4). Necropsy revealed that the double spine and partially duplicated thoracic and abdominal cavities were covered by a single integument. There was a single but enlarged heart, which had two aortae emanating from the left ventricle, and there were two caudal vena cavae returning to the right atrium. One trachea was present which inserted into partially duplicated and enlarged lungs. There was a single sternum but two sets of rib cages. The lateral rib cages united with the sternum while the medial cages were partially fused to each other Fig. 4. Close-up of Fig 3 showing abnormal curvature of the spine. Ó 2006 The Authors. Journal compilation Ó 2006 Blackwell Verlag Craniothoracopagus in a Dog without relating to the sternal floor. The diaphragm was highly extensive while the abdominal cavity was partially duplicated with a corresponding duplication of the medio-lateral contents of the abdomen. There was fusion on the median plane, thus there was a duplication of the spleen, pancreas and the intestines while there was an anastomosis of the two sets of ileum at the midline. The two stomachs were fused along the lesser curvature while the liver appeared larger than normal and extensive. There were four kidneys, two were superficial (each on the extreme left and right) and the other two relatively median kidneys were located behind the intestines and were smaller. The pelvic bones, bladder and genital systems were duplicated. Dissection of the head revealed one mandible, a single frenulum and an elliptical tongue that appeared larger than normal (macroglossia). There was cleft palate (palatoschisis). A single row for the molar pads was present. Also present were the lateral retropharyngeal lymph nodes, which were bilateral. The ligamentum nuchae had one origin before branching into two. Discussion Teratogenesis in conjoined twins arises as a result of incomplete fission during the process of twinning (Nichols, 1979). According to Roberts (1986), they are most common in cattle occurring once in every 100 000 births but rarely seen in sheep, pigs, dogs, cats and horses. Usually, the specific causes of these abnormalities are unknown but they are known to be due to genetic factors (e.g. chromosome abnormalities), environmental factors (such as drugs, plants, viruses, etc.) or by both the above-mentioned factors (Hiraga and Dennis, 1993; Moore and Persaud, 1993; Cazabon and Adogwa, 2003). In the cow, toxic plants, trace elements, infectious agents and physical agents such as hyperthermia, undue pressure during rectal palpation in early pregnancy and irradiation have been identified as teratogens (Saperstein, 2002). This case could have been due to a genetic mutation as only the twin puppies were affected. However, it could also have been caused by physical or environmental factors as the dam was allowed to Ó 2006 The Authors. Journal compilation Ó 2006 Blackwell Verlag 181 stray around the neighbourhood in search of food. The occurrence of palatoschisis is usually associated with such congenital abnormalities (Isitor and Adogwa, 1992; Corbera et al., 2005). The death of the other puppies in the litter could have been the result of asphyxiation caused by prolonged labour and obstruction caused by the conjoined twins. This is probably the first report in the literature of craniothoracopagus in a dog. We advise that veterinarians, commercial dog breeders and owners be aware and report such cases to ascertain a more accurate incidence of such congenital abnormalities in dogs. Dog owners and commercial breeders should also be advised against using dogs with a history (or lineage) of congenital abnormalities for breeding. References Cazabon, E. P. I., and A. O. Adogwa, 2003: A case of cephalothoracopagus in sheep in Trinidad and Tobago. Can. Vet. J. 44, 56–58. Corbera, J. A., A. Arencibia, I. Morales, and C. Gutierrez, 2005: Congenital duplication of the caudal region (monocephalus dipygus) in a kid goat. Anat. Histol. Embryol. 34, 61–63. Hiraga, T., and S. M. Dennis, 1993: Congenital duplication. Vet. Clin. North Am. Food Anim. Pract. 9, 145–158. Isitor, G. N., and A. O. Adogwa, 1992: A case of calf craniopagus in Trinidad. Vet. Rec. 130, 401–402. Moore, K. L., and T. V. N. Persaud, 1993: The Developing Human: Clinically Oriented Embryology, 5th edn. Philadelphia, PA: W.B. Saunder’s Company. Nichols, B. L., 1979: Conjoined Twins in Birth Defects Compendium, 2nd edn. London and Basingstoke: Macmillan Press Limited. Noden, D. M., and A. de Lahunta, 1985: The Embryology of Domestic Animals, Development Mechanisms and Malformations. Baltimore, MD: Williams and Wilkins. Roberts, S. J., 1986: Gestation period: embryology, fetal membranes and placenta. In: Veterinary Obstetrics and Genital Diseases (Theriogenology), 3rd edn (S.J. Roberts, ed). Ann Arbor, MI: Edwards Brothers, p. 51. Sadler, T. W., 2000: Langman’s Medical Embryology, 8th edn. Lippincott: Williams and Wilkins. Saperstein, G., 2002: Congenital defects and hereditary disorder in ruminants. In: Large Animal Internal Medicine, 3rd edn (B. P. Smith, ed.). St Louis, MO: Mosby, pp. 1465–1555.