A congenital defect of the distal forelimb of a cat and of a dog.

A sterilised, female calico domestic cat, weighing 4 kg, was presented to a private practitioner for examination. Her mother had produced her first and only litter, comprising 6 kittens, at the age of 3 years. Apart from this particular cat, all of the kittens appeared to be normal. The cat presented appeared to have no problems apart from the structure of her right forelimb, which she did not use when walking. The distal portion of the forelimb appeared to be duplicated, and the tips of each of the 2 rays bore digits with claws. One small digit was present on the medial ray and 2 longer digits on the lateral ray. She used the other 3 legs for locomotion, and was able to jump through an open window, higher than 1 m off the ground. The elbow was fixed in a flexed position. She was first examined by the reporting veterinarian at an age of 3 years, as she was ill, weak and unable to jump to even a small height. Either cystitis or an unknown urinary bladder complication was suspected, and she was treated with amoxycillin (Clamoxyl RTU, Pfizer) parenterally and orally for 5 days. She was returned for re-examination less than a month later, as she was still struggling to jump and suffered from urinary and faecal incontinence. Initial improvement was observed after injecting her with 10 mg prednisolone (Kyron), and dispensing 5 mg prednisolone tablets (Be-tabs, Pharmaceutical Pty Ltd) and Extract of Green Lipped Mussel (Compass Distributors) at 125 mg per day. Her improvement lasted for 2 months, after which she deteriorated again, suffered from faecal and urinary incontinence, and was euthanased at the owner’s request. Photographs of the forelimb of the cat (Fig. 1) and the X-ray image are presented here (Fig. 2). The duplicated lower portion of the right forelimb can be seen. An X-ray revealed that the radius and ulna had developed in such a way that they formed 2 complete compartments that were separated by skin to halfway up the shafts. The olecranon of the ulna had dislocated proximally and the bones involved in the joint were fused. The proximal shaft of the ulna had bent around the distal end of the humerus. The distal end of the ulna was deformed and the carpal bones were disrupted. Only the first digit was present at the distal end of the radial side of the forelimb, and digits 4 and 5 were present on the ulnar side. The proximal joints of the digits attached to the ulna were hyperflexed and the distal joints were hyperextended. The digit attached to the radius projected out straight. A 4-year-old Boerboel bitch, born of registered parentage, was presented at the same veterinary practice and another apparent duplicat ion of forel imb elements was observed. In this case, the digits of her left forepaw were deeply separated between the 3rd and 4th rays, and all 5 rays were visible externally (Fig. 3). The owners reported that she would shake this paw at first in the morning but would then walk and run quite normally.