Feline plasmacytic pododermatitis is an uncommon disease affecting either the metacarpal or metatarsal footpads. Rarely, digital footpads may be affected.
The cause is unknown, although the disease may be immune-mediated based on the frequent finding of hypergammaglobulin Aemia, plasma cell infiltration and response to glucocorticoids. Affected cats may be FIV positive.
- Multiple foot pads– particularly the central metacarpal or metatarsal.
- These become swollen and in the absence of ulceration are usually non- painful.
- The pads have a characteristic dough-like, spongy texture and may indent on palpation.
- In light coloured pads a violet colour is frequently seen.
- There are often multiple white striae criss-crossing the pads.
- Some pads may ulcerate, particularly in those cats with access to the outdoors and this will result in lameness, prompting veterinary advice.
- Rarely some cats will also have plasmacytic stomatitis, glomerulonephritis or renal amyloidosis.
The main differential diagnosis is eosinophilic granuloma. This normally affects one pad and does not have the doughy texture on palpation.
In the case of unilateral lesions differential diagnoses include neoplasia, or bacterial and fungal granulomas.
- The clinical picture and physical examination are very characteristic and the diagnosis is straightforward in most cases.
- Hypergammaglobulinaemia is a frequent finding.
- Fine needle aspirates demonstrate numerous plasma cells.
- Biopsy also confirms the diagnosis although it is rarely necessary.
In asymptomatic cats, particularly those kept indoors, observation without treatment is appropriate.
Systemic glucocorticoids are effective in many cases. An initial dose of 4mg/kg of prednisolone is given once daily and then tapered to increasingly lower doses once improvement is noted, usually within three weeks.
Alternatively, dexamethasone 0.5mg once daily, tapering to once every three days, may be effective in those cases not responding to prednisolone.
Cyclosporine (Atopica) may be effective. A dose of 7mg/kg once daily is given until improvement is noted – within 2 to 6 weeks. Following remission the dose is tapered and some cats may remain in remission on every 72 hours dosing.
Doxycycline at 10mg/kg has been used extensively in plasma cell pododermatitis and improvement should be seen within one to two months. The drug should be given in food or with a water bolus to minimise the risk of oesophagitis.
In those cases not responding to medical treatment, wide surgical removal of affected pads is an option.
In the absence of complications such as glomerulonephritis or renal amyloidosis, the prognosis is good.