Veterinary nurses caring for a group-housed colony of research cats noticed a 4-year-old neutered male domestic short hair cat with mild hair loss, and lameness. The animals in this closed research colony had not been vaccinated.

The cat was lame on the left front limb but was otherwise in a good physical condition and free to roam within the colony. The nurses had not noticed other abnormalities previously in this animal.

Physical examination showed enlargement and ulceration of the left carpal footpad (Fig. 1). The affected pad felt soft and pulpy. We took blood for hematology and biochemistry. The cat was feline leukemia virus (FeLV) negative and feline immuno-deficiency virus (FIV) negative. Complete blood count showed anemia (PCV 18.6%) and electrophoresis revealed a polyclonal gammopathy.

Figure 1: Fore limb paw of a 4-year-old neutered male domestic short hair cat with mild hair loss, and lameness.
figure 1

The paw shows swelling of the carpal pad and central ulceration. Photo courtesy of the Post Graduate Foundation in Veterinary Science, Sydney, Australia.

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Based on the clinical findings, we took a biopsy for histopathological examination.

What are your differential diagnoses for this condition? What is your likely diagnosis and how would you confirm it? What are the available treatments for this condition? What is the prognosis?

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