Page 190 - Canine Lameness

162 12 Distal Limb Region

12.6.4.1 Pemphigus Foliaceus
Pemphigus foliaceus is one of the most commonly reported immune-mediated dermatoses in dogs
DISTAL LIMB REGION When it occurs on the footpads, it may cause lameness, because of changes to the pad that include
and is known to affect multiple sites, but in rare cases the footpad may be the only site affected.

thickening due to swelling and hyperkeratosis with scaling, crusting, hardening, and fissuring
(Mueller et al. 2006). Severe cases may exhibit purulent exudate from beneath hyperkeratotic foot-
pad crusts. Cytology of purulent exudate may demonstrate acantholytic keratinocytes. Diagnosis is
generally confirmed by histopathology.

12.6.4.2 Superficial Necrolytic Dermatitis
Superficial necrolytic dermatitis, also called “necrolytic migratory erythema” and “metabolic epi-
dermal necrosis,” is an uncommon skin disorder associated with a systemic disease. Although
most commonly ascribed to a hepatic disease (hepatocutaneous syndrome), it is also associated
with pancreatic glucagonoma, phenobarbital use, and intestinal conditions. Hypoaminoacidemia
appears to be the common pathophysiological pathway. Shetland Sheepdogs, West Highland White
Terriers, Cocker Spaniels, and Scottish Terriers may be predisposed. Older animals are most com-
monly affected. Lameness and licking of the footpads are often the first signs of the condition.
Typically affecting all the feet, superficial necrolytic dermatitis may also cause the pads to become
hyperkeratotic, crusted, and fissured with secondary bacterial infections. Occasionally the skin of
the muzzle, perineum, elbows, or hocks is also affected. Diagnosis is confirmed with skin biopsy.
Elevated liver chemistry values and ultrasound confirming hepatopathy when accompanied by
pad and skin lesion are highly suggestive of the syndrome (Outerbridge 2013).

12.6.4.3 Paw Pad Hyperkeratosis
Hyperkeratosis of the footpads is familial in Irish Setters, Kerry Blue Terriers, Dogue de Bourdeaux,
and Golden Retrievers, but may also be associated with canine distemper virus (Duclos 2013). The
condition affects all pads and generally presents in 4- to 6-month-old puppies. It is characterized
by a defect of keratinization, causing excessive keratin of the paw pads (Figure 12.9B). The paw
pad keratin presents as hard vegetative, feathered, and fissured projections of horny tissue. Some
affected individuals may be very lame. A tentative diagnosis can be made based on the signalment
and clinical appearance, but confirmation requires histopathology. An idiopathic nasodigital form
which also involves the nasal planum is described in Labrador Retrievers.

12.6.4.4 Zinc-responsive Dermatoses
Zinc-responsive dermatosis is a systemic keratosis that may result in thickening, scaling, and crust-
ing of the pads in approximately one-third of affected dogs (White et al. 2001). Similar changes are
seen on other areas of skin, particularly the facial skin. The condition is described in genetically
predisposed breeds such as Siberian Huskies and Alaskan Malamutes, as well as in rapid growing
large- and giant-breed puppies fed zinc (Zn)-deficient diets. The disease may require biopsies to
confirm the diagnosis (Outerbridge 2013). In genetically predisposed animals, supplementation
with elemental Zn is often curative. In the dietary deficient cases, correcting the diet is curative.

12.7 Conditions of the Digit/Paw Skin

12.7.1 Interdigital Web Injuries
Interdigital web injuries have been most clearly described in racing Greyhounds (Blythe et al.
2007) but can occur in any breed of dog. Injuries include laceration, stabs, foreign body penetra-
tions, and splits between adjacent digits. Such injuries often heal slowly and are vulnerable to