Definition
Pododermatitis is inflammation of the skin of the foot. Affected tissues may include interdigital spaces, foot pads, nail folds (paronychia), claws, or other tissues of the foot. There are many potential causes and therefore presentations of inflammatory foot disease.
Cause
The initiating cause of pododermatitis is not always known. Key potential causes of inflammatory foot disease include:
- Trauma: foreign body or local trauma (chemicals, physical trauma from stones etc, clipper burn); intense licking (for example due to allergies)
- Immune mediated: auto-immune; hypersensitivities (contact irritation, atopic dermatitis and food allergy); idiopathic (for example sterile granulomas)
- Parasites: hookworm, demodicosis, ticks and trombiculids (harvest mites)
- Iatrogenic: drug reaction
- Infection: bacterial infections; fungal infections including Malassezia, Candida, etc; osteomyelitis; canine distemper
- Psychogenic (behavioural)
- Localised neoplasia
- Idiopathic
Signalment and history
Can affect dogs of any age or type. Some groups or breeds are reported to be more commonly affected.
- Short-coated breeds
- Basset hound, Boxer, Bull Terrier, Dachshund, Dalmatian, English Bulldog, German Shorthaired Pointer, Great Dane, Mastiff, Weimaraner
- Sterile granulomas may be more common
- Long-coated breeds
- German Shepherd, Irish Setter, Retrievers, Pekinese
- Clipper trauma may be more likely
- Working breeds
- Trauma or foreign body may be more likely
- 'Highly strung' breeds
- Psychogenic lesions (behavioural cause) may be more common
- Breeds predisposed to allergic skin disease
- Lesions may be accompanied by other signs consistent with the underlying disease process such as atopic dermatitis
Scarring from previous episodes may increase risk of recurrence. History of worming, housing and lifestyle may also indicate the likely cause (for example hookworm migration)
Clinical signs
One or more feet may be affected. Front feet are more commonly affected and the dog may be lame.
Lesion distribution can vary with underlying cause:
- Asymmetrical (for example single foot affected); trauma; excessive licking; infection (bacterial or fungal) including osteomyelitis; demodicosis; neoplasia
- Symmetrical: contact irritant; immune mediated (allergies, auto-immune, drug reaction, sterile granuloma); immunosuppression or immunodeficiency (inherited or acquired) especially if several feet, not pruritic, recurrent or non-responsive to treatment; infection (viral, for example distemper); demodicosis
- Nail/claw lesions: nail sloughing (auto-immune or immune mediated, bacterial); nail deformity (for example primary seborrhoea in Cocker Spaniels)
- Footpad lesions (significant involvement): auto-immune; drug reaction; zinc responsive dermatitis; canine distemper virus
Lesions that may be observed
- Erythema and oedema
- Nodules, ulcers, fistulae, exudate. Note: some nodules may be scars from earlier lesions
- Alopecia particularly from licking
- Brown salivary staining from licking
- Swelling of feet or metacarpal/metatarsal areas
- +/- pain pruritus paronychia (inflammation of skin around nail)
- Lesions are often consistent with the underlying skin disease
Examples of pododermatitis presentations
Demodicosis
- Differential diagnosis for any pododermatitis
- May present as pododermatitis only
- Possible indication of immunosuppressive disease, for example hypothyroidism
- Mites may persist in feet despite extensive miticidal therapy
Allergic dermatitis (for example atopic dermatitis)
- Salivary staining from excessive licking is common
- Commonly involves the interdigital spaces, nail folds or the back of the feet
- Secondary infection (bacteria or Malassezia) common
Bacterial infections
- Staphylococcus intermedius commonly involved
- Lesions often focal, papular or pustular with crusts and draining tracts
Sterile granulomas/pyogranulomas
- Multiple firm nodules or plaques, with or without alopecia, inflammation and ulceration
- Lesions may also be present on the head
Pemphigus complex (auto-immune disease)
- Inflammation or crusting at the pad-skin junction
- May develop severe hyperkeratosis, crusting and erosion
- Pustules in severe disease
- Interdigital region and nail folds are commonly involved
- Varying pain and lameness
Vasculitis (inflammation of the blood vessels)
- Focal erosive lesions often to the central pad
- +/- abnormal nail growth
- +/- other skin lesions (ulcerations, oedema, etc)
Diagnosis
- Careful history and physical exam
- Include full body examination for evidence of systemic or generalised skin disease
- Note lesion distribution and type
- Comprehensive diagnostic skin tests (where cause has not been immediately identified in Step 1)
- Speed of resolution is important to minimise scarring
- Multiple disease components may be present (for example secondary infections)
- Skin scrapings +/- trichogram. Multiple scrapings/trichograms are required (Demodex mites can be hard to find in the feet)
- Cytology to identify bacteria and Malassezia
- Fungal culture (dermatophytosis)
- Skin biopsy: may be required for diagnosis of demodicosis especially in thickened skin; histopathology, for example for neoplasia, foreign body or auto-immune disease
- Radiographs
- Suspected bone or joint involvement, for example osteomyelitis, neoplasia
- Foreign body identification
- Contrast radiography for suspected lymphatic or arterial disease
Treatment and management
Treat quickly to minimise scarring. Treatment depends on underlying cause.
Infectious disease
- Treat identified causes
- Parasites: treat with appropriate parasiticide. For Demodex, prolonged treatment may be required
- Bacterial/fungal infections: draining lesions should be soaked twice daily for 10–15 minutes until drainage has stopped, for example in epsom salts (magnesium sulphate). Treat with appropriate antimicrobial, topical and/or systemic medications. Consider depth of lesions, duration of treatment and spectrum of activity required. Monitor bacterial lesions via palpation (deep lesions are slower to heal than surface lesions). Prolonged antibiotic courses (for example 8–12 weeks) are commonly needed
- Monitor and reassess
- Investigate for potential underlying disease if incomplete resolution or recurrence, for example immunosuppression or allergic skin disease. Treat and manage underlying cause (for example hypothyroidism, atopic dermatitis)
- Surgical debridement may be required especially if resistant to medical treatment alone (for example chronic scarring)
- Long-term management
- Chronic scarring predisposes to further disease
- Protective boots or restricted activities may minimise recurrence
Immune-mediated disease
- Allergic dermatitis (for example atopic dermatitis, food allergy, contact allergy)
- Vasculitis
- Pemphigus (auto-immune)
- Idiopathic sterile granulomas or pyogranulomas
- Treat secondary or underlying infections
- Identify any underlying cause
- Manage as for underlying cause
- Symptomatic therapy
- Appropriate anti-inflammatory/immunosuppressive medication
Other
Manage as appropriate for underlying disease
