What's wrong with that foot? (Proceedings)
Plasma cell pododermatitis
The etiology of this unusual condition in cats is not known. It probably falls into the category of other lymphoproliferative disorders of cats.
Clinical signs include soft, puffy swelling of one or more of the footpads. The metacarpal and metatarsal pads are most frequently affected. The condition usually affects more than one foot but occasionally unipedal involvement is observed. Surprisingly, affected feet do not seem to be painful unless ulceration of the pads occurs. Secondary infection may occur in ulcerated pads.The clinical appearance is fairly classical if several feet are involved. Confirmation can be made by fine needle aspiration (FNA) or biopsy. The aspirate will usually include numerous RBCs mixed with plasma cells and some neutrophils. Neutrophils may be more numerous if there is secondary infection in an ulcerated pad.
Occasionally this condition will regress spontaneously, however, treatment is recommended. Doxycycline (10 mg/kg PO q24h) may be effective, most likely because of its anti-TNFα effects. Glucocorticoids (oral or repositol) will usually produce regression. Other immunosuppressive drugs such as cyclosporine may be helpful but have not been used as often. The prognosis for recovery from this condition is good.
Cutaneous horns are composed of keratin overgrowth. They may affect one or multiple footpads. Often thin and horn-like (hence the name), they may appear like second "nails" close to the nails on the digital pads. If not on a weight bearing surface, these lesions usually do not cause lameness. If on the plantar surfaces of the pads, they may cause discomfort in walking.
Cutaneous horns may be spontaneous, and this is often the case on the footpads. Horns are also associated with papillomavirus infection, FeLV, and squamous cell carcinoma. Diagnosis of the condition is usually based on the appearance of the lesions. Affected cats should be tested for FeLV because this is an easy rule-out diagnosis. Single horns associated with scaly skin lesions should be biopsied to rule out SCC.
If the horns are not causing lameness the lesions are often ignored. The horny growth can removed by trimming, however, the horns will often recur. Horns causing discomfort should be removed and, if it is possible to do so without causing a large pad defect, the base of the lesion should be excised to prevent re-growth.
Lung carcinomas in cats may metastasize to the digit, usually the third phalanx, to cause bony lysis, painful, firm swelling of the toe, and paronychia. If a single digit is involved, the swelling is often attributed to infection and the underlying lesion may not be recognized until routine therapy fails to alleviate the problem. Lesions may occur in multiple digits and that should alert the astute clinician to look at the lung early in the course.
Radiographs of affected digits usually demonstrate bony lysis of the third phalanx with significant soft tissue swelling. As is typical of neoplasms, the bony lysis usually does not cross the joint space to the second phalanx but periosteal reaction may be seen in this area. Lung radiographs may reveal a single pulmonary lesion or diffuse lung carcinoma.
Excision of the affected digit(s) may help alleviate pain, however, the primary lesion is in the lung and microscopic metastasis to other digits or other body areas may already be present. Treatment of the primary lung tumor will not improve the condition of the feet. Therapy is therefore usually palliative and consists of analgesia and supportive care. NSAIDs may be beneficial because of their analgesic/anti-inflammatory effects as well as COX-2 inhibitory activity. COX-2 is involved in tumor angiogenesis and these drugs may slow tumor growth. Drugs that have been used in cats include Piroxicam (0.3 mg/kg PO q24-48h) and Meloxicam (0.1 mg/kg X 1-2 days, then 0.1 mg [total dose] PO q24-72h). As with the use of any NSAID, renal function should be closely monitored to avoid renal toxicity with these drugs.