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WHATS YOUR DIAGNOSIS
Diagnosis | Interdigital cyst
Interdigital cysts are firm, raised subcutaneous inflammatory lesions found in and on the interdigital webs of the paw. The cause is usually a traumatically ruptured hair follicle. The surrounding inflammation of the skin and subcutaneous tissue is due to a foreign-body reaction to the keratin and hair.
Current opinion suggests that interdigital cysts result from a combination of allergies, conformation, breed (shorthaired dogs are more commonly affected), and trauma caused by licking1. Atopy or food allergies can cause pruritus of the limb extremities and dogs lick their paws to alleviate the itching. Interdigital cysts are often seen in dog breeds predisposed to atopy, such as West Highland White Terriers2. Licking the pruritic area causes hair shafts to break, leaving the base of hair shaft in the skin and leading to a foreign-body reaction. Short-coated, deep-clefted, big-boned dogs, such as Great Danes, also seem especially predisposed to interdigital cysts3. (Interestingly, this affected beagle was the largest and heaviest beagle in its age group). The foot mechanics of big-boned dogs predisposes them to developing interdigital cysts because they end up bearing weight on hair-producing skin of the footpad. Veterinary dermatologists often try to address the poor foot mechanics in these dogs with supportive booties that tighten the foot up and bring weight back on to the footpads2.
In research beagles, interdigital cysts are common but usually not accompanied by clinical signs. They tend to occur on front rather than hind feet4. Affected dogs are not lame and astute technicians often detect the cysts during grooming or clinical examination. Kovacs et al.4 completed a retrospective analysis of risk factors by using the clinical records from 743 research beagles at their research site. They examined multiple factors, including age, gender, weight, body condition score (BCS), cyst location, and type of cage flooring. They found that age, BCS, and the type of flooring were all significant factors in the occurrence of inter-
digital cysts. No cysts were found on dogs younger than 1...