Figure 4.

Metastases from primary lung tumours are not the only lesions that can affect the digit, or multiple digits, of cats. Infectious agents living in the environment (eg, Nocardia species, mycobacteria, fungi) and fastidious agents inoculated by biting rodents (rats, mice, voles) can also produce digital infections that tend to be granulomatous or pyogranulomatous in nature. Of course, these infections usually do not have associated lesions evident in chest radiographs, and cytology of aspirates or histology of excisional biopsies almost always reveals the aetiological agent. It is interesting that some infectious agents that spread haematogenously (like cryptococci) can also involve digits and other tissues that tend to be involved in the ‘lung–digit syndrome’. These images show (a and b) feline leprosy due to Mycobacterium lepraemurium; note the different severity in different toes of the same cat; (c and d) Nocardia species infections in two cats; (e) Cladosporium species infection; note that the lesion has a bluish hue imparted by the presence of this pigmented fungus in the cat’s tissues. Courtesy of Richard Malik (a–d), Joanna White (c and d) and Eamonn Lim (e)