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CLAW DISEASES IN DOGS AND CATS


Nail disorders are relatively rare in companion animals, particularly in comparison with nail disorders in man ^(1-6), which are numerous and related to various causes ⁽⁷⁾. Anatomy of the canine claw unit has been well described ^(1,8,9,10).

Clinical signs ^(1-4)

Onyxis is by definition the disease of the abnormal looking nail. It can be proximal, distal or it may involve all the nail. It may affect only one nail or be multiple depending on the cause. Perionyxis is the inflammation of the nail fold. Onychoschisis means fissuration (splitting) of the nail. Onychorrhexis is the breaking of a nail which has become brittle. Onychogryphosis is a deformation of the claw. It appears to be elongated and distorted. Onychomadesis is the sloughing process of nails. Onychoclasis is the fracture of the claw. Trachyonychia is a nail disorder in humans characterized by lustreless, longitudinally ridged and rough-surfaced nail plates. Pruritus is rarely observed in nail diseases. Pain is more common. However neither pruritus nor pain will be noticeable in many cases such as onychogryphosis. 

Diagnostic approach

This shall be based on history, physical examination and complementary diagnostic aids, including biopsy by amputation or without onychectomy ⁽¹¹⁾.

Consideration of particular diseases ^(1-4,9)

Traumatic onyxis is a very common disease in the dog. It usually affects only one nail, in particular the thumbnails (digit 1) on the hind legs. The nail is more or less distally broken and pain is usually observed. Diagnosis is clinically obvious. Therapy consists in promptly removing the distal part of the nail with forceps. A bandage is then applied for a few hours. If this is done a few days after the fracture, systemic antibiotics should be used for a week to prevent secondary bacterial infection.

Bacterial onyxis exists in the dog but is much rarer in the cat. In the latter, it is usually associated with an immunodeficient state (FeLV and/or FIV infection, diabetes mellitus etc...). In the dog, it may be idiopathic or secondary to an underlying disease (such as hypothyroidism, or even Cushing's disease). Perionyxis, onychoschisis, onychorrhexis and onychomadesis are usually seen on several nails, with pain as the primary complaint. Diagnosis is made by cytology-which reveals a bacterial pus (degenerated neutrophils, phagocytosis), bacteriology and the response to therapy. Treatment must be based on the removal of broken nails, topical antibacterial therapy and long term systemic antibiotic therapy (based on bacterial cultures and sensitivity testing, Staphylococcus sp. and Gram negative rods often being cultured). Months of careful therapy are needed, until the distal abnormal part of the nail has disappeared. In all cases, and particularly in chronically relapsing ones, an underlying disease should be suspected and, if found, treated. Bacterial pododermatitis, whatever the cause, often leads to bacterial onyxis. Good examples are interdigital pyodermas due to demodicosis and allergic skin diseases. Perionyxis is a prominent feature in such cases. Therapy appropriate to the causal pododermatitis will cure the nail problem if carried out for long enough.

Dermatophytic onyxis is a rare cause of onyxis and perionyxis in the dog, usually with one or a few digits being affected. In Aquitaine, Microsporum gypseum and Microsporum canis have been found to be the dermatophytes which most frequently cause fungal onyxis. Alopecia of the corresponding digit is often observed. Diagnosis is made by Wood's light examination which may reveal the fluorescence of the hair of the digit involved, direct examination and fungal culture of this hair, and histopathology of the nail itself. Skin biopsy and the removal of the third phalanx are unnecessary. PAS staining of the nail is mandatory and reveals the invasion of the nail keratin by the fungal hyphae. Long-term antifungal therapy (griseofulvine, ketoconazole, itraconazole) is necessary until the abnormal part of the nail disappears distally. This may take several months. Other cutaneous lesions should be topically treated simultaneously. Dermatophytic onyxis appears to be extremely rare in the cat. The author has never made such a diagnosis in a feline.

Malassezia perionyxis can be seen in atopic dogs, with a brownish staining of the claw, a greasy exudate in the claw folds and persistent pruritus (12). Malassezia pachydermatis and Candida albicans can be isolated from claws of Bull Terriers affected with lethal acrodermatitis (13).

Onychogryphosis is a classic symptom of canine leishmaniasis. In the enzootic area such a complaint justifies serology and/or a parasitological examination (skin and/or bone marrow cytology). Comprehensive therapy (Lomidine®, Glucantime®, amphotericin B, allopurinol) and a strict follow-up are mandatory.

Onychorrexis and onychomadesis can be seen in chronic cases of pododermatitis caused by ankylostomiasis. Diagnosis is made by cutaneous histopathology and coproscopy.

An inflammatory skin disease of the digits (pododermatitis) is observed clinically in canine atopic dermatitis and food allergy or intolerance. Onychogryphosis is frequent, often associated with perionyxis and redness of the hair on the digits. The nails may appear reddish in dogs whose nails are normally white but this may be due to secondary Malassezia infection. A diagnosis is obviously reached by evaluating all the symptoms observed in these diseases, by skin-testing, serology and elimination diets. Therapy includes allergen eviction, hyposensitization and symptomatic treatment (systemic glucocorticoids, antihistamines, essential fatty acids, topical antipruritic agents etc.).

Auto-immune (and immune-mediated) dermatoses usually affect several digits.

Discoid lupus erythematosus is a not so uncommon cause of onyxis in the dog (3,9,14). In fact, as the disease is symmetrical, as focal thickening and smudging of the basement membrane zone are not seen and as direct immunofluorescence testing is negative, Danny SCOTT named this disease «Symmetrical Lupoid Onychodystrophy» in 1995 (15). It is a real interface onychitis. Onychorrhexis and onychogryphosis are the main features of the disease. Other lesions may be seen in other areas of the body, but this is not always the case. Perionyxis is not always pronounced and skin biopsies of the nail bed area may be unrewarding. Amputation of the third phalanx is often the only way to reveal the typical hydropic and lichenoid interface dermatitis. Alternatively, a 8mm punch biopsy of the nail fold can be performed. This technique is applicable mainly to interface onychitis (it seems that in other conditions the resistance of tissues is higher). Immuno-suppressive doses of glucorticoids (prednisolone) may control the disease. Vitamin E and essential fatty acids (omega-3/omega-6 commercial compound) have been reported to be effective in some cases (3,15,16).

Nails and nail beds may be affected in pemphigus vulgaris (17). Onychogryphosis and onychomadesis can be observed. Severe perionyxis is also present, with erosions around the nail bed which are a source of pain. Diagnosis is made by histopathology either by skin biopsies around the claw or alternatively by amputation of the third phalanx. Biopsies of lesions in other body areas may be diagnostic. Only a guarded prognosis should be made. Immunosuppressive therapy should be carried out (glucocorticoids, azathioprine).

Onychogryphosis and perionyxis can be observed in canine pemphigus foliaceus, particularly in severe forms of the disease. A unique case of pemphigus foliaceus restricted to the claws has been diagnosed by E. Guaguère and J.P. Magnol (9). When pemphigus foliaceus is exclusively confined to the footpads onychorrhexis is often observed. The author has seen 2 cases of pemphigus erythematosus confined exclusively to the footpads, with onychorrhexis. Diagnosis can be made by histopathology. In the extensive forms of the disease (pemphigus foliaceus), biopsy of the skin lesions may be diagnostic. In the localized forms, biopsy of the footpads and/or an amputation of the third phalanx may be diagnostic. Immunosuppressive therapy is necessary.

In the cat, pemphigus foliaceus is a possible cause of severe perionyxis. A thick pus is discovered in the nail bed. Diagnosis is usually made by skin biopsy of the other skin lesions. Glucocorticoid immunosuppressive therapy is helpful.

Severe multiple onychomadesis and/or severe onychogryphosis with ulcerative perionyxis may be seen in the bullous pemphigoid group skin disease (a group of auto-immune disorders with subepidermal clefting as a common feature). They may even be the prominent features of this disease, making it a most painful one. Diagnosis is made by biopsy of the skin lesions, particularly of the digits, if there is ulceration around the nail bed. Alternatively, amputation of the third phalanx of an affected digit may be the only way to diagnose such a condition if only nail disease is present. In one case, the author had the luck to establish a diagnosis of bullous pemphigoid by removing nails from a dog with onychomadesis; a small amount of skin tissue still attached to the claw displayed the typical lesions of dermal-epidermal clefting. Therapy is not easy. Glucorticoid immunosuppression is not always helpful.

Systemic lupus erythematosus, cold agglutinin disease, drug eruption and vasculitis may affect the claws (3,4).

Trachyonychia has been seen in a dog with alopecia areata (18). A cat affected with pseudopelade had onychomadesis (19).

In Man, Raynaud's disease is due to a spasm of digital arteries due to cold, which may be either secondary (e.g., to SLE) or idiopathic. It is a cyanotic/hyperhaemic and painful disease. Three female dogs (2 Boxers of 3 and 4 years of age and a 5 year-old mongrel) were suspected by the author to have a Raynaud-like disease (9). The patients were in severe pain from several digits which from time to time looked cyanotic. Onychogryphosis was prominent. Skin biopsies were performed in 2 dogs around the claws and showed non specific superficial dermatitis and a few Malassezia in the stratum corneum in one dog. Direct immunofluorescence testing was negative for IgG and C3. ANA test was negative in the 3 dogs. Long term therapy with isoxsuprine, a vasodilatator, at the dose of 1mg/kg/day, was very helpful.

Idiopathic onychomadesis has been described in dogs (11,20,21) although some of these cases could be undiagnosed cases of interface onychitis, particularly when biopsies were not done.

Keratinization diseases: the author has seen severe multiple onychogryphosis in cases of canine ichthyosis. However, generalized skin lesions were prominent and histopathology of the lesions confirmed the diagnosis (9). Many cases responded partially to retinoid therapy.

Some cases of zinc responsive dermatosis observed in Nordic dogs involve several digits. Two cases restricted to the digits, with a prominent perionyxis and above all onychorrhexis were observed by the author in Malamutes (of 10 and 12 months of age respectively) (9). Diagnosis was made by histopathology, with biopsies taken around the nail bed. There was a dramatic response to zinc sulfate supplementation (15 mg/kg BID) whereas zinc methionine had not been very helpful.

Several cases of idiopathic nosodigital hyperkeratosis in the older dog may be associated with mild multiple onychogryphosis.

Genodermatoses. Ichthyosis is a hereditary keratinization disorder. Onychogryphosis can be seen in canine dermatomyositis (Collies, Shetlands, Beaucerons) and epidermolysis bullosa (Beaucerons) (22). Glucorticoids, vitamin E and pentoxifylline are helpful. A similar hereditary condition could exist in the cat, with onychomadesis (23).

A case of congenital linear epidermal nevus ending in the paw of a hindleg was diagnosed by the author in a 3-year-old Pyrenean shepherd, with a prominent onychogryphosis on 2 digits (and a secondary demodectic pododermatitis as well). The nevus responded well to retinoid therapy (etretinate 1 mg/kg/day during 18 months followed by acitretin, at the same dosage, during 8 months).

Idiopathic onychogryphosis is observed in dogs. It usually affects one digit. Diagnosis is made by the elimination of other possible causes. Regular removal of the nail affected is advisable. The author has seen multiple inverted papillomas in a 7-year-old mixed French Spaniel associated with a severe onychogryphosis of only one digit. Papillomas can cause the development of cutaneous horns and potentially this claw alteration was linked to the skin disease.

Neoplasia of the nail fold is a common cause of onyxis and onychomadesis in the old dog. Squamous cell carcinoma (which is often misleading since it looks like a non-healing wound), melanoma, and mast cell tumour are relatively frequent. However, nailbed epithelial inclusion cyst, keratoacanthoma, inverted papilloma, and eccrine adenocarcinoma may also be observed (3,24). These tumours affect only one digit usually, and necessitate aggressive excision therapy. Melanoma and mast cell tumour may metastase, although squamous cell carcinoma has a better prognosis than usually believed if excision is carried out at an early stage. Swelling is often prominent and pain is acute. Diagnosis is made by histopathology of the removed tumour and radiographs of the digits often reveal bone lysis. Multiple squamous cell carcinomas are seen in black dogs, affecting several digits, with a slow growth rate and rare metastasis (3,25). Excision therapy is mandatory. Nail bed tumours are rarer in old cats. Those that do occur are squamous cell carcinoma, hemangiosarcomas, and metatasis of primary lung carcinomas (4,24).

CONCLUSION

Claw diseases in dogs and cats are often diagnostic and therapeutic challenges. A detailed case history, a thorough physical examination and appropriate complementary examinations are required to establish a diagnosis. The latter include cytology, bacteriology, mycology, histopathology (skin biopsy around the nail bed or even third phalanx amputation, sometimes very helpful) and immunological tests such as skin-testing and elimination diets. Therapy must be specific. In all cases appropriate follow-up is most important.

Web site
Didier-Noël Carlotti, Doct.-Vét., Dip ECVD 
Cabinet de Dermatologie Vétérinaire
Bordeaux-Mérignac, France

TORN DEWCLAWS 

Dewclaws are the "fifth finger" on the dog's front legs. Since dogs essentially walk on their toes, the dewclaw — the dogs thumb — usually dangles uselessly several inches above the ground. The dewclaw can catch on brush, logs, rocks, or other trail obstructions the dog has to navigate over, under, or around. A torn dewclaw can bleed a lot, but generally it isn't a serious injury. The prescribed treatment is to stop the bleeding through direct pressure. Next, wrap gauze around the dewclaw and leg, then wrap tape around it to hold the dewclaw firmly to the leg. Don't wrap too tightly, however, or you'll constrict blood flow into the lower leg. 

TOENAILS

Overgrown or overly short toenails can cause limping. This is particularly a problem in older, less active pets. These nails often break off exposing the quick of the nail. These nails quickly become infected. In other cases, overgrown toenails twist the joints of the toes causing toe arthritis, and painful toe joints. These nails need to be clipped off short under a mild anaesthetic. Antibiotics are rarely required. Very active dogs and dogs housed on concrete often wear their toenails down to the quick. With time, the quick on these nails recede and pain subsides.
Since nails can grow at the rate of 2mm per week, nails which are not worn down can eventually penetrate the underside of the toe. If excessively long, nails can be traumatized by everyday use. There are also a number of infections and diseases associated with the special fold of skin around the base of the claw. Nails should be clipped using specialist nail care products on a regular basis.

FEET

The skin on the feet is the most favoured site of skin diseases such as atopic dermatitis and many others. If the paws are not regularly exercised from youth, growth abnormalities and claw problems can result in specific irritations which may make the foot prone to infection. Likewise, over-use, such as excessive walking on roads by dogs, can lead to tenderness and infection. There are dry skin treatments available in such cases. 
Check your dog’s feet regularly to make sure that there are no splinters or infections in the paw area. The best way to know if there is any infection is to make sure that there is not any unusual smell or excretion coming from the paws. Just like humans though, dogs can pick up splinters and get cuts on the soles of the feet. Usually if something like this has occurred, you will know because you dog may seem in pain or be limping. If you dog appears to be in pain, or you believe it might have an infection the best thing to do is to take it to the vet. 
In most dogs the feet are a very hardy area and not prone to many problems. It does however depend on the breed of your dog, as some are more prone to problems than others. It is always best to speak with the breeders or someone where you got your dog from to know what is involved in the upkeep of your particular breed of dog. Alternatively check with your local vet as to what you should be doing to care for your type of dog. For the most part as long as your dog’s feet are kept clean and you check them and trim the claws occasionally and any necessary hairs, then your pet should remain happy and have healthy feet. 

Unlike human nails, which are good for trapping dirt and not much else, your pet's nails go to work nearly every day -- digging holes, climbing trees, and scratching posts. They take quite a beating, and sometimes they crack and splinter. For a dog or cat, cracked nails are not only painful but also prone to hard-to-treat infections, which can cause even more cracking. 

Nails usually crack for the simple reason that they got too long, says Nancy E. Wiswall, D.V.M., a veterinarian in private practice in Bethesda, Maryland. Since all of your pet's nails grow at roughly the same rate, more than one will often crack at one time, she adds. 

Though they don't look or feel like skin, nails are really an extension of the skin layer. Anything that causes unhealthy skin, like dietary or immune system problems, can also cause cracked nails, says Dr. Wiswall. Pets eating low-quality food will sometimes develop cracked nails because they are not getting all the nutrients that they need, she adds. 

In dogs, a condition called lupoid onychodystrophy (also known as 20-nail disease) can cause all the nails to fall out. When they grow back, they will usually be brittle and prone to cracking, says Grant Nisson, D.V.M., a veterinarian in private practice in West River, Maryland. Vets aren't sure what causes this condition, although it may be related to the immune system, he says. 

See Your Vet If... 

• More than one nail is cracked

• Your pet's nails fell out and then grew back cracked

• Your pet has begun having trouble walking, getting up, or climbing stairs

• One or more legs is dragging

• He has a limp that doesn't go away

• One or more legs is in an awkward position

• There is swelling in the toes, feet, or legs

• Your pet can't get up

• Your pet is constantly licking or biting his feet

• The nails are broken, cracked, or bleeding

• There are cuts, blisters, growths, or burns on his paw pads

• Your pet is lame first in one leg and then another

• He has pain when jumping off a bed or changing position 

WHAT TO DO WITH A TORN TOENAIL


It is best to have your veterinarian examine your dog's injured toenails. 

Suddenly you notice – there’s blood on your dog’s paw and he is limping and licking his paw. When you take a closer look you see the problem – a terrible torn toenail. Toenail problems, specifically torn or broken nails, are common in dogs but rarely life-threatening. Nevertheless, they are quite painful.

Nails often get snagged on fabric or carpet fibres, and in an attempt to dislodge the attached material, your dog might pull away, tearing the nail in the process. You might not even notice until you see blood or your dog begins to limp or cry. If left untreated, a torn nail can bleed intermittently and become infected, not to mention the pain and irritation for your dog.

Veterinary Care
Some torn nails can be treated at home if your pet will allow it, but veterinary care can reduce the potential for infection and provide easy removal of the torn nail. Depending on the extent of the tear, removal of the nail at the level of tear is usually sufficient. This is most easily done with nail trimmers. After removal of the broken part, your veterinarian may apply a temporary bandage to stop bleeding. He may also prescribe an antibiotic to prevent infection.

Home Care
If you try to treat your dog at home, remember: a torn nail is painful for your dog and you should take care to avoid getting bit. The following steps are important:

• Initially, you will have to stop the bleeding. You can use silver nitrate or styptic pencils. If you don’t have either of these, try cornstarch or flour. When placed on a bleeding nail, these generally stop the bleeding.

• Removing the loose nail is the most difficult part of caring for the torn nail. Most often, you can just yank the loose piece of nail off very quickly. If the nail doesn't come off easily, you can try to use a pet nail trimmer and remove the nail at the level of the break. Remember, this will probably hurt your dog for a second. If the tear in the nail is high up and near the base of the nail, don't attempt to remove it with trimmers. If the nail isn't easily pulled off, see your veterinarian for treatment. The last bone of each toe is very close to the beginning of the nail. Without experience, you may end up hurting your dog more than you realize.

• If you successfully remove the damaged part of the nail, gently wash the area with warm water to remove any debris lodged between the nail and the toe or leg. Then apply a temporary bandage if necessary for bleeding. Take care not to wrap the bandage too tight so circulation will not be damaged. Leave it in place for 12 to 24 hours.

• If you do not feel comfortable taking care of a torn nail, call your veterinarian. Leaving a torn nail to heal on its own (which will not happen) or allowing the nail to grow out is not a recommended option. This causes persistent irritation and possible repeat breaks. 

Preventative Care
The best preventative care is to trim your pet’s nails frequently. Overgrown nails are most commonly affected.

A Common Problem by: PetPlace Veterinarians

PEMPHIGUS/SYMMETRICAL LUPOID ONCHODYSTROPHY (SLO) 

A fairly common autoimmune disease in greyhounds is Pemphigus, also know as symmetrical lupoid onchodystrophy (SLO), which causes loss of the toenails. Pemphigus also involves the footpads and interdigital skin (between the toes), whereas true SLO involves only the nails. Treatment of these diseases can be frustrating and is often misdiagnosed as fungal or bacterial. Unfortunately, the only way to definitively diagnose pemphigus/SLO is by amputating the end toe bone, including the nail, as a pathologist can make the diagnosis only by observing the skin/nail junction. But this unnecessary and expensive approach is somewhat radical when there are other solutions. 

Treatment with prednisone to target the underlying autoimmune disorder is by far the most effective and can result in dramatic improvement in comfort within the first few weeks of treatment. Combined with chlorpheniramine (an antihistamine) to control the itching of the skin around the nails, the use of prednisone can make a marked difference in this disfiguring, uncomfortable disease. The most popular dosage for this in greyhounds is 15 mgs of prednisone daily for a week and then tapering to 5 mg every other day for long term. The chlorpheniramine is in 4 mg tablets. (This information is from Suzanne Stack, DVM, of Arizona. Dr. Stack has been involved in the treatment of racing and retired racing greyhounds for several years.)

Health Concerns in the Retired Racing Greyhound
By Judy Kody Paulsen, Founder, GCNM

TOENAIL LOSS IN DOGS

Lupoid onychodystrophy is a disease in dogs that causes them to lose their toenails. A research team studied the effect of fatty acid supplementation (for example, fish oil or primrose oil) in treating dogs with this condition. This study compared the fatty acid concentrations in the blood and nails of normal and affected dogs. Studies showed an improvement in the conditions of dogs with lupoid onychodystrophy, but researchers don't know if the improvement is due to the anti-inflammatory characteristics of fatty acids or if affected dogs developed the condition because of a fatty acid deficiency.

SYMMETRICAL LUPOID ONYCHODYSTROPHY

Claw disorders in the dog that are restricted just to the claw are rare in clinical practice. Bacterial or fungal infections may be seen, but there is to much emphasis placed on dermatophytes, as this seems to be rare in clinical practice. Such infections will also have swelling and exudate present around the digit (paronychia). Cytology of this exudate may reveal micro-organism such as bacterial but they should be intracellular to be considered highly significant. Autoimmune diseases of the nails will usually have additional lesions on other areas of the skin.
Symmetrical lupoid onychodystrophy is the most common disease of the nails seen in practice. The term symmetrical indicates 2 or more feet are involved. Oncychomadesis (sloughage of the nail) may eventually involve all 20 nails. The nails appear painful before they are lost, but afterward seem fairly well tolerated. The underlying etiology is unknown but autoimmune causes as well as infections or vaccinations have been suspected. There is no known breed or sex predisposition, but my clinical impression is that large breeds (especially German shepherds and Labrador retrievers) seem predisposed. The term lupoid is used due to microscopic changes of affected nails, although there is some debate on how significant these microscopic changes really are. Nevertheless some of the therapies used for discoid lupus patients have resulted in benefit for these patients. A combination of tetracycline and niacinamide (each at a dose of 500 mg three times a daily) along with high dose of fatty acids such as EFA caps or Derm caps (at twice the manufactures dose for treating atopy) are used. Anaesthesia followed by removal of the nail and leaving the exposed nail base will certainly reduce the pain. Many patients will respond, but owners should be advised that several months will be necessary before a response is seen. New nails usually grow in normal. As other forms of lupus require long term treatments I recommend therapy for life, which certainly necessitates an accurate diagnosis. After a good clinical response is seen, I will usually recommend decreasing the dosage to once daily. Amputation of P3 of all the nails is also described as an option, however most of these patients do respond to conservative medical care.

Article by Thomas P. Lewis II, DVM, Diplomate, ACVD, Board Certified Veterinary Dermatologist