SLO in dogs (symmetric lupoid onychodystrophy) is a condition that causes a dog’s nails on multiple feet to become brittle, crack, and eventually slough off. Integrative veterinarian Dr. Julie Buzby explains the causes, breed predispositions, symptoms, diagnosis, treatment, and prognosis for SLO in dogs to help dog parents be informed about this condition.
As dog parents, we’ve probably all experienced a toenail injury with our dogs at some point. Whether it’s a nail that was accidentally clipped too short or a dewclaw that got torn off during a crazy game of fetch, even one damaged nail can cause considerable discomfort for our sweet dogs. Thankfully, though, most of the time, toenail injuries heal quickly and are soon forgotten.
However, for some dogs, a single painful claw may be just the beginning of a much more serious condition known as symmetric lupoid onychodystrophy (SLO).
What is symmetric lupoid onychodystrophy (SLO) in dogs?
Symmetric lupoid onychodystrophy (pronounced LOO-poid ON-ick-o-DIS-tro-fee) is an uncommon disease that affects the toenails and nail beds of dogs, causing brittle, abnormal nails that may slough off. SLO usually starts off only impacting one toenail. But the condition can progress quickly over a few weeks to the point where it involves multiple nails on all four feet.
Note: Some veterinarians use the term “onychitis” or “onychomadesis” interchangeably with “onychodystrophy” when describing this condition.
What causes SLO in dogs?
Veterinarians may not always be able to identify the exact cause of SLO, which is why they often classify it as an idiopathic disease. Researchers suspect that a hereditary component exists in several dog breeds. Additionally, certain immune-mediated diseases, including autoimmune thyroiditis (inflammation of the thyroid gland), have been implicated in the onset of SLO. And some believe SLO could be an immune-mediated disease, too.
Which dogs get symmetric lupoid onychodystrophy most commonly?
SLO typically affects middle-aged dogs, but it can occur at any age. There have been cases in dogs as young as two years old.
With a few exceptions, symmetric lupoid onychodystrophy predominantly occurs in large breed dogs, including:
- Akita
- Bearded Collie
- Cavalier King Charles Spaniel
- English Setter
- German Shepherd Dog
- German Shorthaired Pointer
- Giant Schnauzer
- Gordon Setter
- Greyhound
- Labrador Retriever
- Rhodesian Ridgeback
- Rottweiler
- Welsh Corgi
- West Highland White Terrier (Westies)
Interestingly, Bearded Collies, German Shepherds, and Gordon Setters have been identified as carriers of abnormal genes that predispose them to SLO. More specifically, a study showed that having certain forms of the DLA class II gene increases the risk of SLO in Gordon Setters.
What are the symptoms of SLO in dogs?
Early on in the disease, SLO has clinical signs that could fit with many conditions. Usually, the first symptom you’ll notice is your dog licking his or her paws incessantly. At the time, you might think seasonal allergies in dogs, a dog paw yeast infection, or another more common problem is to blame.
However, as the disease progresses, dogs will show the hallmark sign of SLO—sloughed claws and other nail abnormalities that affect more than one paw and/or multiple nails on one paw. You may notice the following changes in the nails:
- Nails appear dry and brittle
- Flaking, cracking, or splitting of nails
- Nail lifting away from the underlying nail bed (sloughing)
- Missing nails with exposed nail bed
- Crooked or abnormally shaped nails
If symmetric lupoid onychodystrophy has been going on long enough, sloughed nails may start to regrow. These new nails are usually brittle and flaky. Plus, they may grow or curl in odd directions due to the underlying inflammation of the nail beds.
Additionally, affected dogs may experience:
- Lameness: You may notice your dog limping or moving abnormally.
- Pain: If you touch your dog’s foot, he or she may pull away. Plus, your dog may spend a lot of time licking the feet and nails.
- Bleeding around the nails: Sometimes affected nails start to bleed.
- Secondary bacterial infections of the claw beds: Redness, inflammation, or discharge in the nail fold at the base of the nail can signify a secondary infection.
Head to the vet if your dog has abnormal nails
If you are seeing some of the symptoms above or are otherwise worried about your dog, please make an appointment with your vet. Nail injuries and conditions like SLO can be painful. Plus, some tumors of the toe or nail bed change the appearance of the nail. Thus, it is important to have your dog seen sooner rather than later.
How will the vet diagnose a dog with SLO?
As discussed earlier, SLO can resemble many other conditions in its early stages. Because of this, vets consider it a diagnosis of exclusion, meaning they will want to rule out other conditions first.
Other common conditions that would also affect multiple nails and feet include allergies, infections (bacterial, fungal, or a combination of both), systemic autoimmune disorders (such as pemphigus, lupus, or vasculitis), and adverse drug reactions. Nail trauma and nail bed cancer can mimic early SLO in dogs, too, but only affect one or two toes. These are the sorts of problems your vet will want to rule out.
If your veterinarian suspects that your dog may have symmetric lupoid onychodystrophy, he or she will likely recommend a variety of diagnostic tests. Your vet can perform most of the tests in-house. But he or she may refer you to a to a board-certified veterinary dermatology specialist in some cases.
Potential diagnostic tests include:
Cytology of the nails and nail beds
To perform cytology, the vet will swab the area under and around the nail base with a sterile swab. Then he or she will transfer the collected sample to a microscope slide, stain it, and examine it. Cytology is useful for identifying fungal or bacterial organisms.
Bloodwork
Baseline blood tests for dogs can help detect infection, abnormal organ function, or more serious conditions like cancer. Plus, checking your dog’s thyroid function can help rule out immune-mediated thyroid inflammation, a potential contributor to SLO.
Bacterial culture and sensitivity
The vet may submit a sample for a culture and sensitivity to help guide antibiotic selection. Commonly identified bacteria may include Staphylococcus, Pseudomonas, or E. coli.
Fungal culture
Yeast (Malassezia organisms) and certain types of ringworm (such as Trichophyton and Microsporum species) have been identified in nail infections. If the vet thinks there could be a fungal component, he or she will perform a fungal culture.
Elimination diet trial
If the vet suspects a food allergy in dogs, he or she may recommend an elimination diet trial. This involves feeding the dog a novel or hypoallergenic diet and nothing else for 8-12 weeks. During that time period, the vet and dog parent will monitor the dog closely to see if the symptoms improve.
Punch biopsy of the nail bed
While the dog is under light sedation, the vet will collect a core sample of tissue from the nail bed with a small biopsy punch (which looks like a tiny cookie cutter). Then he or she will send the sample to the laboratory. There, a veterinary pathologist will examine the tissue under the microscope. Punch biopsies are a good way to detect inflammation, infection, and soft tissue cancers.
X-rays
If the dog has severe lameness or abnormal changes to the shape of the toe(s), the vet might recommend X-rays of the foot. They can help identify a bone infection (osteomyelitis) or bone cancer (osteosarcoma in dogs).
Biopsy of the tip of a severely affected toe
Amputating the tip of a toe and submitting it to the laboratory for analysis can help confirm whether or not cancer is present. However, this is a more invasive diagnostic test, and not every veterinarian will recommend it. For dogs who do undergo amputation, the vet only removes the small bone at the end of the toe (called P3), which supports the toenail and nail bed.
After evaluating the results of the diagnostics and ruling out other similar-appearing conditions, the vet may make a diagnosis of SLO. Then he or she will discuss the treatment options with you.
What is the treatment for SLO in dogs?
Typically, treating SLO involves using a combination of medications and nutritional supplements. Plus, dogs with more severe cases may need surgical intervention.
Medical management of SLO
Often, the vet will start the dog on several of the following treatments:
- Essential fatty acid supplementation (EPA/DHA): Both omega-6 and omega-3 fatty acids for dogs help decrease inflammation and control the overactive immune response. Your vet can calculate the dose of omega fatty acids that is right for your dog.
- Vitamin E: The anti-inflammatory and antioxidant properties of vitamin E can be beneficial for dogs with SLO.
- Niacinamide: This supplement (also known as Vitamin B3) is often given in combination with antibiotics. After tapering to the lowest effective dose, it’s safe to use long-term as a maintenance therapy for dogs who cannot completely stop treatment.
- Antibiotic therapy: Vets often prescribe tetracycline or doxycycline in conjunction with niacinamide. This combination has the ability to modulate the immune response, which is helpful if there is an immune-mediated component.
- Pentoxifylline: This medication is a vasodilator (increases the diameter of blood vessels). It improves blood flow to nail beds and helps decrease inflammation in the surrounding tissues.
- Immunosuppressants: These medications include corticosteroids (prednisone for dogs), azathioprine, and cyclosporine (Atopica®). Vets usually reserve them for severe cases that do not respond to other treatment regimens.
- Pain medications: Since SLO can be painful, the vet may prescribe non-steroidal anti-inflammatories (NSAIDs) like carprofen for dogs to help keep your dog comfortable. If the dog can’t take NSAIDs due to being on steroids or for another reason, the vet can also use other pain medications such as gabapentin for dogs.
- Frequent nail trims: Your veterinary team will likely recommend frequent nail trims (as often as every two weeks). This can help minimize new cracks and fissures that might develop in your dog’s nails.
Rechecks with the vet and patience are important during medical management
During treatment for symmetric lupoid onychodystrophy, the vet will carefully monitor the new nail that is growing at the nail bed to see if it is becoming more normal. (The old, dry, cracked, or twisted nails will not change in response to treatment.) It often takes about three to four months to see improvement in the nails, and sometimes even as long as a year.
This is a slow process because until the nail grows out some, you can’t necessarily tell if the treatment is working. If it isn’t, your vet will try a new therapy and then wait to see what happens.
Sometimes it takes a combination of therapies or some trial and error to find what works best for a particular dog. Also, if a dog develops side effects to a medication, the vet will have to alter the plan. While you understandably want your dog to be feeling better ASAP, it is important to be aware of how patient you will need to be during the treatment process.
Assuming your dog responds well to treatment, your vet will typically have you start to slowly taper the medications after about the first six months of therapy. Gradually decreasing the dosage over time allows you to closely monitor your dog for the recurrence of clinical signs. Should that happen, the vet will adjust the medication plan accordingly.
Some dogs may require lifelong therapy for SLO even if their symptoms do improve with medication.
Surgical treatment of SLO
Surgical treatment for SLO involves removing the affected nail(s) while your dog is under sedation. Following the procedure, the exposed nail beds will be very sensitive and painful. Typically, your veterinarian will prescribe pain medication to help keep your dog comfortable as the toes heal and the nails begin to regrow.
Occasionally, the vet will recommend amputating the nail entirely (removing the nail, nail bed, and last bone of the digit). However, this is not necessary for most cases and is a more extreme measure.
Keep treatment goals in mind
Having normal nails again would be great (and sometimes does happen). However, the ultimate goal of treatment is to manage the inflammation and keep your sweet dog as pain-free as possible. This might mean getting to the lowest effective dose of the medications and then staying there, not trying to get your dog off all medications and supplements. Understanding that can help you have realistic expectations as a dog parent.
What is the prognosis for dogs with SLO?
Dogs with SLO usually have a good long-term prognosis with consistent treatment and prompt management of flare-ups. This doesn’t mean that SLO will be cured, as many dogs will need medication long-term and/or will continue to have somewhat abnormal-looking nails. What it does mean is that appropriate management gives your dog a good chance of not continuing to have painful, sloughing nails.
If your dog’s nails still look a bit wonky, but they aren’t cracking or sloughing, and your dog is comfortable, that counts as a win.
Partner with your vet
A diagnosis of SLO can be a bit overwhelming since it’s such an unusual condition. It is understandable to have questions about treatment and concerns for your dog’s long-term comfort. As always, working closely with your veterinarian or a veterinary dermatologist is the best way to keep symptoms under control and ensure that your sweet dog continues to be as happy and healthy as possible.
Has your dog been diagnosed with SLO?
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