Concurrent claw problems are not unusual in many skin diseases, but rare as the only dermatological problem. The most common
disease affecting single claws are: trauma, bacterial or fungal infections; the most common condition affecting multiple claws
would be onychodystrophy. The claw is important for the pet for grasping and holding, moving and used as a defense tool. For
this reason it is important that the claws are regularly trimmed and healthy. Diseased claws will predispose to trauma, abnormal
locomotion, pain, lameness, and pododermatitis. Various medical terms are used to describe the claw lesion such as: Paronychia
(inflammation or infection of the claw fold), Onychodystrophy (abnormal claw formation), Onychogryphosis (hypertrophy and
abnormal curvature of claw), Onychomadesis (sloughing of claws), Onychomalacia (softening of claw), Onychomycosis (fungal
infection), and Onychoschizia (splitting of claw).
If a patient is presented with a claw disease a detailed history (e.g. vaccine can induce vasculopathy; started with one claw
and is spreading typical for symmetric lupoid onychodystrophy) should be obtained and a thorough inspection of the affected
claw should be performed. Cytology is very important and simple test to identify bacteria and yeast, which are very often
a cause of secondary infection in abnormal claws. Bacterial and fungal culture is required if initial antimicrobial therapy
did not cure the infections. Biopsies are usually required if multiple claws are affected and a systemic and immune-mediated
diseases or neoplasia are suspected.
Trauma is the most common cause for claw diseases in dogs and sometime in cats. Typically one or few claws are affected. In
rare cases claws on all four feet are affected, which can occur due to excessive running on asphalt, concrete and gravel,
or the use of infected nail clippers. Untreated claw trauma will often result in secondary bacterial infections.
The distal part of the affected nail should be removed and the foot bandaged if necessary. In older lesions with suspected
infection, foot soaks with disinfectants, and oral antibiotics in more severe cases is recommended.
Bacterial claw diseases
Bacterial claw infections are common and are considered a secondary problem. The most common underlying cause is trauma. However,
systemic diseases such as hypothyroidism, Hyperadrenocorticism, diabetes mellitus, hypersensitivities, immune-mediated diseases
and onychodystrophy may cause claw infections. Chronic severe infections of the nail bed can result in permanent defective
claw growth. Swelling of the nail bed area, pain and pus formation is typical. Cytology is the preferred diagnostic method.
If the infections does not respond to initial antibiotic therapy a bacterial culture & sensitivity may be necessary.
To treat infected claws it is best to remove as much of 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 normal claw is covering the previously
Fungal claw diseases
Fungal infections are rare and organisms which have been reported to claw and often the nail bed diseases are: Malassezia,
dermatophytes (especially Trichophyton), followed by blastomycosis, cryptococcosis, sporotrichosis. Dogs with Malassezia infections
show brown-red 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 antifungal therapy. Itraconazole and terbinafine
have shown to accumulate in keratin, horn, and hairs.
Parasites such as Demodex do not affect directly the claws, but will result in secondary changes due to persistent inflammation
and secondary infections if not treated appropriately. Demodex mites are often difficult to find on skin scrapes from pedal
skin, due to their deep follicular localization in those areas. Sometimes skin biopsies are necessary to confirm a demodicosis
on the feet. Other parasites which have been reported to cause onychogryphosis are Leishmania and hookworms, which may require
specific laboratory test to confirm the disease.