246 (21)

The dermatological examination is concemed with whether one or both feet are affected, the presence of pruritus, Identification of lesions and their distribution on the feet and elsewhere.

If only one foot is involved, microbial agents (e.g. dermatophytes, Trombicula autumnalis lamę, Demodex spp., or yeasts), physical factors^1,4 (e.g. a bum or trauma), or Chemical agents^1,4 (e.g. caustic substances) should be suspected. Tumours such as sąuamous celi carcinoma, fibrosarcoma (Fig. 24 : 24) and digital metastasis of a pulmonary adenocarcinoma^,8, and in rarer cases, behavioural causes (e.g. anxiety), should also be considered. If morę than one foot (or even all the feet) is involved, the above dermatoses should not be excluded but the possibility of a bacterial cause (multiple paronychia, linked to retroviral infection ^U4 (Fig. 24 : 25,26)), allergy (e.g. atopic dermatitis, food intolerance or mosquito bite hypersensitivity), auto-immune dermatosis (e.g. pemphigus foliaceus), or even a tumour (e.g. trichofolliculoma) (Fig. 24 : 27) should also be investigated.

The presence or absence of pruritus is an important part of the clinical examination. Pruritic pododermatoses are initially suggestive of an allergic dermatosis ¹⁶ (e.g. atopic dermatitis, food intolerance or mosąuito bite hypersensitivity), one of the clinical forms of the eosinophilic granuloma complex (e.g. eosinophilic plaąues or granulomas), a parasitic dermatosis¹² (e.g. trombiculiasis), a viral or post-viral dermatosis (e.g. herpesvirus ^l4, poxvirus ¹³ or herpesvirus-associated erythema multiforme ^l5), a specific bacterial infection (e.g. nocardiosis, actinomycosis or botryomycosis), deep fungal infection ¹¹ (e.g. histoplasmosis or sporotrichosis) or even a skin condition associated with a behavioural disorder ^M. Non-pruritic pododermatoses would suggest dermatophytosis, demodicosis, a tumour or even congenital hypotrichosis

Identification of pedał lesions, although not all of eąual diagnostic significance, can often steer the clinician towards a group of dermatoses. Erythema and scaling are freąuently observed in dermatophytosis, trombiculiasis, allergic dermatitis (e.g. atopic dermatitis or food intolerance), or demodicosis. Erosive lesions suggest an allergic dermatosis, trombiculiasis (even if Trombicula autumnalis larvae cannot be identified) or an irritant contact dermatitis. Ulcerative lesions suggest an auto-immune dermatosis, a specific bacterial infection (e.g. nocardiosis or actinomycosis), a deep mycosis, a cutaneous drug reaction, poxvirus infection, herpesvirus infection, junctional or dystrophic epidermolysis bullosa, or a tumour. Crusting is often seen in notoedric mange, auto-immune dermatoses such as pemphigus foliaceus and systemie lupus erythematosus, and herpesvirus-associated erythema multiforme. Nodular lesions might indicate eosinophilic granulomas (Figs 24 : 28,29), plasma celi pododermatitis ^1,4 (Figs 24 : 30-33), specific bacterial infections (e.g. atypical mycobacterial infection, leprosy, nocardiosis and actinomycosis) or deep mycosis.

Assessing the pedał distribution of lesions involves a detailed examination of the digits, interdigital spaces, the ventral surface of the feet, the footpads, the ungual pads and the claws. Involvement of the digits and interdigital spaces would suggest dermatophytosis, trombiculiasis, demodicosis, an allergic dermatosis, a specific bacterial infection, a deep mycosis, or a tumour (e.g. sąuamous celi carcinoma, trichofolliculoma, fibrosarcoma or metastasis of a pulmonary adenocarcinoma). Involvement of the ventral surface of the feet, less common than in the dog, would suggest an allergic dermatosis, eosinophilic granuloma complex lesions (e.g. eosinophilic plaąues), trombiculiasis or less commonly notoedric mange. If the footpads are affected, the following conditions should be suspected: an auto-immune dermatosis (e.g. pemphigus foliaceus), plasma celi pododermatitis, eosinophilic granuloma, irritant contact dermatitis, a deep bacterial or fungal infection, morę rarely, dermatophytosis, herpesvirus-associated erythema multiforme or dystrophic epidermolysis bullosa. If the ungual pads are affected, bacterial paronychia linked to retroviral infection (especially when multiple), calicivirus infection, trombiculiasis, dermatophytosis, cryptococcosis, an allergic dermatosis, an auto-immune dermatosis (e.g. pemphigus foliaceus or systemie lupus erythematosus), or morę rarely a dermatosis linked to a behavioural disorder should be considered. Multiple claw involvement is rare and would suggest dermatophytosis (onychomycosis), or morę rarely an auto-immune dermatosis (e.g. pemphigus foliaceus), or nail chewing linked to anxiety or depression. An extremely rare cause would be absence (or rudimentary presence) of claws in congenital hypotrichosis (seen in Birmans) or junctional epidermolysis bullosa (seen in the Siamese) (onychomadesis).

Lesion Identification in other parts of the body will help the clinician to strengthen his/her clinical suspicions.