Symmetric Lupoid Onychodystrophy in Dogs

What is symmetric lupoid onychodystrophy?

Symmetric lupoid onychodystrophy (SLO), also known as idiopathic onychomadesis, is an uncommon condition that causes abnormal nail growth, resulting in malformation, breakage and loss in dogs. It typically affects multiple or all nails.

What causes SLO?

SLO is considered idiopathic, which means the cause is unknown; however, it is thought to be immune-mediated, with the dog’s own immune system attacking the growth area of the nail. There may be a genetic component as well, because certain breeds appear to be predisposed to the condition (e.g., bearded collies, Gordon setters, German shepherds, and rottweilers). A thyroid condition (autoimmune thyroiditis) may also result in SLO.

What are the signs of SLO?

The first sign of SLO is often the loss or breaking off of one or more nails. Usually, there isn’t an obvious cause for the break or any inflammation around the site of the break. Over a short time, all the nails become brittle and break off. When the nails regrow they are brittle and misshapen, discolored, and likely to split or break again. The nails may develop discharge or swelling from secondary infections. As split or broken nails are sensitive, your dog may lick their feet, limp, or be hesitant to walk.

How is SLO diagnosed?

SLO is considered a diagnosis of exclusion, meaning other conditions that can cause clinical signs must be ruled out first. Your veterinarian will review the history of your dog’s condition, examine your dog, and may recommend diagnostic tests, including:

• Skin cytology: Sampling the area around the nail to look for bacteria or yeast
• Fungal culture
• Bacterial culture and sensitivity to identify an infection and determine the most effective antimicrobial treatment
• Radiographs (X-rays) to look for disease in the bone, like infection (osteomyelitis) or cancer
• Thyroid testing may reveal autoimmune thyroiditis or hypothyroidism
• An elimination diet trial, if your veterinarian suspects your dog has an abnormal response to something in their diet
• Nail biopsy (surgically removing the nail) may reveal signs of other disease (this procedure may be recommended if there is a strong suspicion of cancer)

How is SLO treated?

SLO can be successfully managed with medication, but some nails may remain malformed and easily breakable. Regular, frequent nail trims are important in reducing painful nail breakage.

Treatments include:

• Oral fatty acid supplementation with eicosapentaenoic acid (EPA)
• Antibiotics to treat secondary infections
• Oral vitamin E supplementation
• A combination of niacinamide and tetracycline (or doxycycline; may be given for long periods of time, then gradually weaned to the lowest effective dose)
• Pentoxifylline to improve blood flow to the nailbed while decreasing inflammation
• Immunosuppressive treatments, such as corticosteroids (prednisone) or cyclosporine (Atopica)
• Pain medication may be needed
• In severe, non-responsive painful cases, more aggressive immunosuppressive therapy or declawing (removing the nails and the last bone of the toe) may be recommended

Effects of treatment may take up to three months to be seen and treatments may be reduced or, in some cases, discontinued once the condition appears fully controlled. Unfortunately, some dogs require lifelong treatment.