Pododermatitis in cats: how should it be treated?
Introduction
The term pododermatitis in cats is normally used to refer to plasma cell pododermatitis (PCP). Although this disease is considered commonplace in cats, an identical form has been reported very rarely in dogs.2
However, despite being common knowledge for over 40 years, the aetiopathogenesis and management of the disease have not yet been fully clarified.
Aetiopathogenesis of pododermatitis in cats
The aetiopathogenesis of PCP is not well understood and several possible causes have been suggested.
- The fact that in some studies 50% of cats with PCP also had antibodies to feline immunodeficiency virus2 indicates the two processes are connected, although this idea is yet to be proven.
- An association between feline leukaemia virus infection and PCP was described recently in one cat,3 but obviously no overall conclusions can be drawn from this.
- In many cases, PCP responds to treatment with doxycycline, which in principle could indicate an infectious aetiology; however, PCRs of different infectious agents on biopsy samples taken from patients with PCP proved negative.1
- By contrast, in some cats pododermatitis follows a seasonal pattern, which suggests a possible allergic origin.
- Furthermore, in cases with a favourable response to surgical management, it was proposed that the clinical picture could be due to a structural defect.2
In any case, the theory most accepted today, and partly based on the favourable response obtained when patients are treated with immunosuppressive doses of corticosteroids or gold salts, is that PCP is an idiopathic immune-mediated disease and the response to doxycycline may result from its immunomodulating activity.1
Clinical picture
The disease can affect cats of any age (ranging from 6 months to 12 years) and it seems that males may be predisposed. Many cats with pododermatitis are taken to the vet showing signs of lameness, although some animals may be asymptomatic.
Clinically, PCP usually follows a fairly striking course: it starts with a soft swelling of the paw pads, usually affecting several limbs,
although it may also only affect a single paw pad. Inflammation is usually more severe in the central paw pads (both on metacarpals and metatarsals) than in the digital paw pads. More or less linear, whitish hyperkeratotic striae may be observed on the surface of the paw pads.
Ulceration occurs in 25–35% of cases. Lymphadenopathy, lethargy and pyrexia can be observed in some patients.1,2
Diagnosis
The main differential diagnosis of PCP is probably against eosinophilic granuloma, which does not usually affect several paw pads on different limbs and may cause skin lesions in other areas. Other possible differentials for consideration, especially if only one limb is affected, are foreign bodies and neoplasms.2
A presumptive diagnosis of pododermatitis in cats can be made based on the clinical history, physical examination and observation of abundant plasma cells in a cytology study of the affected area.1,2
The definitive diagnosis, particularly when only one limb is compromised, may require a biopsy. A biopsy may only reveal superficial and deep perivascular dermatitis with abundant plasma cells, but this is often accompanied by the infiltration of adjacent adipose tissue and the presence of Mott cells. Fibrosis may be seen in chronic cases.2
Although a cause–effect relationship has not been established, considering that a significant number of patients with PCP are FIV+, it is advisable for all cats with PCP to be tested for feline immunodeficiency virus.
A blood count may reveal neutrophilia, lymphocytosis and thrombocytopaenia, while hypergammaglobulinaemia is the most frequent biochemical disorder.1,2
Pododermatitis in cats: treatment
The treatment of choice for pododermatitis is doxycycline. Although clinical remission has been reported with oral doses of 25 mg/day for 3 to 4 weeks4, 10 mg/kg/day is the current recommendation. With this dose, a complete cure can be expected in a third of cases and a clear improvement in about 80% of animals. The treatment should continue until a complete cure or stable remission is achieved. This usually takes about 10 weeks, although in 10% of patients the disease subsides in 4 weeks and up to 50% achieve clinical remission after 8 weeks of treatment. Cases of spontaneous remission or remission within weeks of completing doxycycline therapy have been reported.2,5
For patients that do not respond to the treatment, they can be given prednisolone at 4.4 mg/kg/day, reducing the dose according to clinical response. Other pharmacological treatments for cases refractory to prednisolone include triamcinolone acetonide( 0.4–0.6 mg/kg/day), dexamethasone (0.5 mg/kg/2day) and cyclosporine (7 mg/kg/day).
Finally, in patients unresponsive to medical management, good responses have been reported with follow-ups for up to 2 years after the excision of the affected tissue.2
Conclusions
Pododermatitis in cats is a rare disease whose aetiopathogenesis is not yet fully clarified. This means its management principally depends on the empirical efficacy of the different treatments. Based on its effectiveness and relatively few side effects compared to other therapeutic options, doxycycline is considered the first-choice treatment.
