Idiopathic symmetric lupoid onychodystrophy (ILSO)

A male neutered three year old Rhodesian Ridgeback dog was presented with a history of all of the nails progressively becoming lose or splitting, including the dew claws, with some nails lost altogether. On physical examination the dermatological findings were limited to the digits with the hind feet having several claws missing and the front feet having a number of dystrophic claws including some with obvious deviations in the dorsal claw material with a transverse line just distal to the claw bed. The dew claws had similar lesions.

The diagnosis is most likely a dystrophic nail condition and histopathological findings may help to confirm the diagnosis of ILSO. The dew claws are the easiest digit to amputate and the whole nail and third distal phalanx should be submitted for histology. In the absence of any history or signs of systemic disease it is difficult to recommend extensive investigation in terms of looking for an underlying disease or trigger factors. So, the test results for blood samples for haematology, serum biochemistry, thyroid function and ANA testing are likely to be normal. Some cases also have fungal cultures performed (usually negative and one would also expect some involvement of the adjacent haired skin which is not the case with ILSO) and bacterial culture of any exudate. In most cases any bacterial isolates are likely to be secondary and treatment may provide little benefit.

This condition is poorly understood and yet very distinct. It is usually seen in larger breed dogs, including German Shepherds, border collies and greyhound-crosses, but may also be seen in smaller breeds including some terrier breeds. It is extremely painful when the nails start to lift off and while pain relief may be helpful it is preferable to sedate/ anaesthetise the dog and remove all of the lose nails, bandage and give a short course of antibacterial therapy combined with NSAIDs for pain relief.

Longer term many cases will have recurrent bouts of nail loss and warrant some kind of intervention. Treatment options may include high doses of oral essential fatty acids (EFAs). This may help to avoid further rounds of claw loss rather than repair of the damaged nail bed. Deformed or dystrophic nails are likely to be a persistent feature of this condition. The most important thing is to reduce the incidence of repeated nail loss because this is a painful process. It may take several months to appreciate that such therapy has helped to prevent the loss of claws given that such losses may only occur every few months. Other treatment options may include pentoxifylline (Trental) or tetracycline and niacinamide and in severe cases possibly glucocorticoids or azathioprine. The nails should be kept short to avoid them being caught and ripped.

© Aiden P. Foster January 23, 2009