Cause: Metatarsal/metacarpal fistulas are due to an immune mediated disease which causes swelling and drainage on the back of the paws just above the large metatarsal and/or metacarpal paw pads.
Affected animals: This condition is most commonly seen in German shepherd dogs (usually male), and sometimes in Weimeraner dogs.
Clinical signs: There is spongy swelling of the skin just above the large metatarsal and/or metacarpal paw pads which develops ulceration and draining tracts which ooze bloody or pus like discharge. If secondary bacterial infection occurs, the inflammation and discharge are increased and the areas may become painful and crusty, causing the dog to lick excessively at the areas. Usually both rear paws and/or both front paws are affected at the same time.
Diagnosis: Microscopic examination of discharge or crusting can document secondary bacterial infection. Biopsy of the area can be performed for definitive diagnosis of metatarsal/metacarpal fistulas.
Treatment: Treatment involves oral +/- topical medications to reduce immune mediated inflammation; this may include initially prednisone/steroids for quicker results, then long term treatment with doxycycline/niacinamide may be helpful (these are oral medications which reduce immune inflammation in a milder, non-immunosuppressive way, but can take 3 months for full effect). Any secondary bacterial infection is treated with oral/topical antibiotics. Additionally, once the initial infection has resolved, topical anti-inflammatory therapy with Protopic (tacrolimus) ointment applied 1-2 times daily to the affected area can be helpful. Refractory cases may respond to oral cyclosporine.
Prognosis: Though every case is different and medications may need to be adjusted depending on response to therapy, metatarsal/metacarpal fistulas are usually a controllable disease; lifelong treatment may be required to prevent relapse.