Hermione, a 3yo female spayed orange domestic shorthair cat, presented for evaluation of swollen, painful paws.
Brittany Lancellotti, DVM DACVD
Veterinary Skin and Ear, Los Angeles, California
History
The owners had noticed waxing and waning problems with her paws for about a year prior to initial presentation, and as the disease progressed, the discomfort began to affect her quality of life. She was primarily an indoor only cat but was allowed some unsupervised time in the owner’s fenced in yard and there were several other cats in the household. She had otherwise been healthy with no major medical concerns. She was FIV/FeLV negative.
Physical exam
On initial presentation, she was bright, alert, responsive and hydrated with a BCS of 5/9. All paws had varying degrees of edema, purple discoloration and white scaling to the paws and digital pads. The pelvic limb paws had multifocal crusts with adhered litter and underlying hemopurulent exudate (Figure 1) with erosions to ulcerations. The remainder of the body was unaffected, including the oral cavity.
Diagnostics
Cytology of the exudate showed severe suppurative inflammation with plasma cells and rare small lymphocytes, hemorrhage, and 20-30 coccoid bacteria per oil immersion field. Complete blood count and serum chemistry had been recently submitted by the primary care veterinarian and, apart from a mild hyperglobulinemia, was unremarkable.
Assessment
Based on the clinical appearance and distribution to multiple paws, she was diagnosed with plasma cell pododermatitis. Doxycycline 5mg/kg twice daily was recommended for immunomodulatory and antimicrobial properties, in addition to gabapentin 10mg/kg twice daily for pain, parasite prevention with selamectin and sarolaner topical solution monthly, daily antimicrobial wipes and an elimination diet trial with a prescription hydrolyzed soy protein diet.
Follow-up
At recheck exam one month later, there was no change in the appearance of the pads. The owner expressed frustration with being unable to administer medications. The pet had received one to two doses of doxycycline per week, rather than twice daily, gabapentin had not been administered and the owner had been unable to perform topical antimicrobial therapy. The pet was, however, receiving parasite prevention and the owner had been able to keep the diet strict. Troubleshooting administering medication to cats was discussed and technicians demonstrated techniques to improve the owner’s confidence and likelihood of success. The treatment plan was otherwise not adjusted.
One month later, the pet returned for recheck and the owner reported improvement. The paws were no longer bleeding and the pet seemed much more comfortable (Figure 2). The owner had still not been able to administer oral medication or use topical antimicrobial wipes. The pet was consistently eating they hydrolyzed soy diet, but the owner complained of loose stools. Use of the Calm and Cozy Cat Wrap was recommended to assist with administration of oral medications to attempt to improve the remaining lesions. To address the loose stools, the diet was switched to an ultrahydrolyzed chicken feather protein diet and a probiotic was recommended.
Two months later, she returned for recheck and the owner had not administered any doxycycline in the previous month. He reported her activity level was fantastic and she had been much more playful than prior to starting treatment. The loose stool resolved with diet change and her food had been strict since the last exam. On physical exam, only one small crust remained on the right pelvic limb paw (Figure 3). Intracellular coccoid bacteria were observed with pyogranulomatous inflammation on cytology from under the crust and cefovecin 8mg/kg subcutaeous injection was administered at that time and two weeks later. The remainder of the paws had resolved edema and no active fissures or crusts.
Figure 4 shows the appearance of the thoracic limb paws at initial presentation (left), and at most recent recheck exam four months later (right). Challenge feeding the diet was discussed, but declined due to how well the patient was managing with diet alone. Based on the owner’s ongoing difficulty with attempting medication administration, as well as the dramatic improvement on diet alone with no noticeable effects to quality of life from the remaining lesions, management was recommended with ultrahydrolyzed diet and parasite prevention.
Discussion
Plasma cell pododermatits (PCP) is a rare disease of cats characterized by infiltration of the paw pads with inflammatory cells, primarily plasma cells, resulting in swollen metacarpal, metatarsal and digital pads with pink to purple discoloration, white striations and erosions to ulcerations that may lead to lameness and secondary infections.1,2 Affected animals may also experience proliferative ulcerative gingivitis and swelling of the bridge of the nose has been reported. There is no age, sex or breed predisposition and multiple etiologist have been suggested, but no definitive cause has been identified. FIV infection has been associated with cases of PCP, but is not a requirement for development of the disease.1,3 PCP has also been classified as an atypical reaction pattern seen with feline atopic sydrome and food allergy.4,5
Definitive diagnosis of PCP is made by histopathology of an affected pad with diffuse dermal and perivascular infiltration by mature plasma cells with or without lymphocytes.1-3,6 Other differentials for single paw lesions include granulomas (infectious or eosinophilic), neoplasia or foreign body reaction. Given the classic appearance of this all four paws with this cat’s presentation, the waxing and waning nature of progression, identification of plasma cells on cytology and the owner’s financial concerns, biopsy was not pursued in this case.
Treatment of PCP involves immunomodulatory medications, such as glucocorticoids and/or doxycycline. Surgical excision of severely affected footpads has been reported to be effective. An elimination diet trial using a prescription hydrolyzed or novel protein diet for at least 8 weeks should be considered due to the potential of food allergy triggering immune stimulation, as was suspected in the current case due to the dramatic improvement on diet alone despite limited medications administered during the treatment period. The prognosis for PCP is generally good, although relapse is possible when tapering medications. Subsequent immune-mediated glomerulonephritis and/or amyloidosis has been reported.6 The current patient showed mild hyperglobulinemia on serum chemistry, which improved following the elimination diet trial, but still remained slightly above reference range. No changes in renal values were observed.
This case reinforces the importance of performing an elimination diet trial in cases of feline plasma cell pododermatitis to investigate the potential contribution of food allergy to the inflammatory reaction. Viral testing should be performed, as well as monitoring of serum chemistry values to evaluate for development of potential secondary renal disease.
References
- Biezus, Giovana, et al. “Plasma Cell Pododermatitis Associated With Feline Leukemia Virus (FeLV) and Concomitant Feline Immunodeficiency Virus (FIV) Infection in a Cat.” Topics in Companion Animal Medicine, vol. 41, Nov. 2020, p. N.PAG.
- Brosseau, Gabrielle. “Feline Plasma Cell Pododermatitis.” Canadian Veterinary Journal, vol. 63, no. 5, May 2022, pp. 545–48.
- Guaguere, E., et al. “FC-23 Feline Plasma Cell Pododermatitis: A Retrospective Study of 26 Cases.” Veterinary Dermatology, vol. 15, Aug. 2004, p. 27.
- Santoro, Domenico, et al. “Clinical Signs and Diagnosis of Feline Atopic Syndrome: Detailed Guidelines for a Correct Diagnosis.” VETERINARY DERMATOLOGY, vol. 32, no. 1, Feb. 2021, p. 26–+.
- Bryan, Jacqueline, and Frank, Linda. “Food Allergy in the Cat: A Diagnosis by Elimination.” Journal of Feline Medicine & Surgery, vol. 12, no. 11, Nov. 2010, pp. 861–66.
- Pereira, PD, and AMR Faustino. “Feline Plasma Cell Pododermatitis: A Study of 8 Cases.” VETERINARY DERMATOLOGY, vol. 14, no. 6, Dec. 2003, pp. 333–37.