Symmetric Lupoid Onychodystrophy

Symmetric Lupoid Onychodystrophy is the most common immune-mediated disease that results in severe claw problems in otherwise apparently healthy dogs.  The disease causes the immune system to become overactive, attacking the nails and nail beds, creating fissured or split nails that never totally heal.  Young adult and middle-aged German Shepherd dogs appear predisposed to this disease.  SLO can appear in all breeds, including crossbreeds and mixed-breeds, although some breeds seem to be more susceptible than others.  It is not infectious or contagious - other dogs which come into contact with it cannot contract it.  It appears to be spontaneous, and there is no evidence of an hereditary factor - because of the absence of studies and the small number of known cases though, there is little proof of this other than anecdotal evidence.

The claw is made up of three general layers. The outside part is hard dead material. In the centre of the claw is the living part, complete with nerves and blood supply, called the ‘quick’. Between the two is a layer of spongy material.  The nail forms at its root, which is located deep inside the toe near the endmost bone of the toe. The newly formed nail grows out towards the external part of the toe for about 3-4 months before it emerges and becomes visible. It takes about 9 months for a nail to grow from root to full length.
 SLO damage occurs while the claw is forming at the root, although the claws usually don’t shed until the damaged part emerges from the toe. As a result, damage you see now actually occurred several months ago, and the results of treatment can’t be assessed for some months after it’s started.

There is usually an acute onset of nail loss.  Initially, one or two claws are lost, but over a course of a few weeks to several months, all claws slough.  Partial regrowth typically occurs, but claws are misshapen, hollow, soft or brittle, discolored, and friable and often slough again. Other symptoms may include: receding quicks, secondary bacterial nailbed infections occur (often with a strong smell), claw splitting (usually down the back of the claw), pain, distorted/twisted claws and lameness. The affected feet are often painful and/or itchy. Affected dogs are otherwise healthy.

This is not the kind of disease that veterinarians see every day, so do not be surprised when a definite diagnosis takes a while to reach.  The information regarding the diagnosis and treatment of all veterinary diseases is too vast for any one veterinarian to memorize.  Veterinarians are usually resourceful getting information about anything they may not be familiar with, so give your veterinarian a chance to help your dog.

Other diseases that need to be considered in the differentials include fungal and bacterial claw infections, autoimmune skin disorders, drug reaction, and vasculitis.  In most instances a diagnosis can be made from visual inspection, however a biopsy of the digit is required for definitive diagnosis.

There are three main methods of diagnosis – diagnosis by aetiology (the characteristics of the disease), diagnosis by response to treatment, and diagnosis by biopsy.

Diagnosis by aetiology
Someone who is familiar with SLO may well be able to make a diagnosis of SLO on sight, particularly if it follows the typical characteristics of the disorder. The possibility of fungal and bacterial infections needs to be eliminated first, as these are more common and can produce similar symptoms. Unsuccessful treatment of bacterial and fungal infections increases the likelihood that SLO is the cause.

Diagnosis by response to treatment
In many cases, where SLO is suspected, the owner or vet may decide against a biopsy and choose instead to commence treatment immediately. The treatments for SLO are quite specific, and usually if the problem responds to the treatment one can consider the diagnosis confirmed.

Diagnosis by biopsy
Diagnosis by biopsy is done by taking a sample of the root of an affected claw and examining it under a microscope. This method is easiest if the dog had affected dew claws, since a dew claw can easily be removed for study.

Until recently, taking a biopsy from a claw other than the dew claws has been a major step for most owners, as it involves amputating the distal phalanx (last bone) of the toe.

More recently there has been a new biopsy technique involving using a biopsy punch to get a sample of the root.

A firm diagnosis can only be reached by the biopsy of a claw, dewclaws usually being used for this.  In the absence of an available dewclaw it is necessary to amputate a toe at its bottom joint in order to do the biopsy.  In many cases, this is considered an extreme step to take, and is not strictly necessary. If the dog is showing signs of SLO, treatment using the latest protocols can be started - if they work, it largely confirms the diagnosis, even without the biopsy.

Treatment is challenging, and can take as long as six months to see positive results. Treat any secondary infections with appropriate antibiotics.  SLO is commonly treated with daily oral fatty acids and oral Vitamin E. Noticeable nail regrowth should be noted within 3 months of initiating this therapy. Other treatments include Tetracycline and Niacinamide, pentoxifylline, and for more severe refractory cases Prednisone and other nonsteroidal immunosuppressive drugs can be utilized.   Removal of claws as they become loose can help to alleviate pain, but generally isn't necessary.  Although there are few studies to scientifically confirm the results, the treatment appears to be effective.  A food allergy has been identified in a few cases of this disease, so it may be appropriate to go through a strict , 8-12 week hypoallergenic food trial.  Bathing the feet in saline or dilute antiseptic solution after walks can often help.  Dog boots can be used to try to prevent lameness during exercise when damaged tissues are painful.  A number of dogs have also been diagnosed with Hypothyroidism at the same time SLO has been diagnosed.  A full thyroid panel may be indicated to evaluate this common hormonal disease.  Once the disease is in remission, supplementation may need to be continued for life to prevent relapse.

The prognosis for nail regrowth is good, although some nails may remain deformed. In some dogs, therapy can be discontinued after 6 months. In other cases, long term maintenance therapy is needed to maintain remission.

Diseases of the Claw and Footpad-A Problem-Oriented Approach SLO Claw Diseases in Dogs

A Retrospective Study regarding Treatment of SLO in 30 Dogs

Symmetrical lupoid onychodystrophy in dogs: a retrospective analysis of 18 cases

Immunohistochemical Evaluation of Mononuclear Infiltrates in Canine Lupoid Onychodystrophy

Canine Symmetrical Lupoid Onychodystrophy
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The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinarian for confirmation of any diagnosis. Your pets life may depend on it.