DERMATOLOGY
the affected claw as possible. Topical antibiotics or
in more severe cases, oral antibiotics should be given
until the lesion is healed and enough until the normal
claw is covering the previously affected area.
Fungal claw diseases
Fungal infections are rare and organisms which have
been reported in claw and often nail bed diseases are:
Malassezia, dermatophytes (especially Trichophyton),
followed by blastomycosis, cryptococcosis, sporotrichosis. Dogs with Malassezia infections show brownred discoloration of the claw with brown-colored
waxy exudate on the proximal aspects of the claws.
This condition is very often seen in dogs with allergies. Diagnostic tests, which will help to identify the
organisms, are: cytology, Wood’s lamp, fungal culture, and biopsy. Most of these fungal infections (except Malassezia) require aggressive systemic anti-fungal therapy. Itraconazole and terbinafine have been
shown to accumulate in keratin, horn, and hairs.
Parasitic diseases
Parasites such as Demodex do not affect the claws,
directly but if not treated appropriately, will result in
secondary changes due to persistent inflammation
and secondary infections. Demodex mites are often
difficult to find on skin scrapes from pedal skin, due to
their deep follicular localisation in those areas.
Sometimes skin biopsies are necessary to confirm a
demodicosis of the feet (due to thickening of the epidermis...Ed) Other parasites which have been reported
to cause onychogryphosis are Leishmania and hookworms, which may require specific laboratory tests to
confirm the disease.
Symmetrical lupoid onychodystrophy
Based on the clinical presentation, inflammatory
pattern and response to therapy, symmetric lupoid
onychodystrophy should be considered an immunemediated disease or vasculopathy. This disease can
occur in different breeds (personally seen in Greyhound, Schnauzer, Labrador Retriever), but German
Shepherds are considered predisposed to this disease.
The problem usually starts with one claw, but within
a couple of weeks other claws become affected. The
animals appear otherwise healthy, but once the claws
start to slough off they become painful, Show lameness, and secondary infections. The claw horn continues to grow, but the horn quality is poor. The claw
appears short, discoloured, deformed, soft and crumbly and tends not to attach well to the underlying nail
bed. (Figure 1) Histopathology (hydropic and lichenoid
interface dermatitis) is usually required to confirm the
diagnosis. Because the histological lesions are located very deep at the claw base, amputation of the 3rd
phalanx may be necessary to be able to diagnose the
disease.
Treatment of this disease requires immunosuppressive
therapy with steroids and high doses of omega-3 and
Figure 1: Symmetrical Lupoid Onychodystrophy demostrating
short, deformed, crumbling, soft nails.
omega-6 fatty acids (e.g. Derm Caps or Omegaderm)
with Vit E, or tetracycline with niacinamide. Improvement and claw regrowth should be noticed within 3-4
months.
Auto-immune diseases
Very rarely auto-immune diseases such as pemphigus
vulgaris, foliaceus or erythematosus may affect claws
besides other skin areas. A biopsy of the nail bed is
usually required to diagnose the disease. As with auto-immune diseases in general, immune-suppressive
therapy is required to manage this disease.
Neoplasia
Among the most common neoplasia involving the
claws, squamous cell carcinoma, melanoma and
mast cell tumors should be considered. Other differentials such as inclusion cysts, keratocanthoma, and
inverted papilloma should be ruled out. In cats, nail
bed tumors are rare, but metastasis of primary lung
carcinoma, hemangiosarcoma and squamous cell
carcinoma have been reported. Tumors usually form
solitary lesions. Melanoma and mast cell tumors may
be aggressive and tend to metastase. All neoplasia
should be diagnosed by histopathology and aggressive excision or amputation of the affected digit is
usually curative.
Miscellaneous rare claw diseases
Idiopathic onychodystrophy affect multiple claws in
older dogs. This condition appears to be predisposed
in Siberian Husky, Dachshund, Rhodesian Ridgeback,
Rottweiler and Cocker Spaniel. Biotic and gelatin may
help to improve the horn quality of the claws.
Idiopathic onychomadesis has been reported in German Shepherd, Whippet, and English Springer Spaniel.
Secondary claw infections are not uncommon. Anecdotal reports suggest the use of pentoxifylline.
Anecdotal reports of diseases such as epidermolysis
bullosa, dermatomyositis, drug eruption, ergotism,
thallotoxicosis, linear epidermal nevi, nutritional deficiencies, disseminated intravascular coagulation, and
necrolytic migratory erythema do exist.
References available on www.vet360.vetlink.co.za
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