- vr 20 mei 2011, 15:35
#2016619
in mijn huidaandoeningenboek staat dit
ook wel genoemd: sterile pedal panniculitis of German Shepherd Dog, deep
metatarsal/metacarpal toritis in German Shepherd Dogs
Clinical features
Metatarsal fistulation of the German Shepherd Dog is an uncommon canine skin disease characterized by well demarcated, frequently symmetric, deep fistulous tracts located dorsal to the midline of single or multiple pawpads (Gross & Ihrke, 1992; Kunkle et al., 1993). The strong breed predilection for the German Shepherd Dog suggests heritability (Gross & Ihrke, 1992; Kunkle et al., 1993; Paterson, 1995; Kristensen, 1997).
The etiology is unknown. Antibodies directed against type I and type II collagen have been noted, suggesting a familial disorder of collagen although details were not given (Scott et al.,2001). German Shepherd Dogs have been bred increasingly for a low, crouching rear stance; the authors speculate that increased strain on soft tissue of the distal extremities (tendons, pawpads, underlying fat pads) may be involved in the pathogenesis.
Some affected dogs have concomitant interdigital bacterial furunculosis, and some have perianal fistulas (Kristensen, 1997); the German Shepherd Dog is predisposed to all three. Genetic linkage between the syndromes may or may not be present. Focal, deep fistulous tracts with well demarcated, slightly swollen, erythematous borders sparingly exude a serous to milky, viscid fluid. Lesions may be either single or multiple. The most common site is dorsal to the midline of the tarsal pad, but lesions may be dorsal to the carpal pads, and very rarely, other pawpads. Deep palpation elicits pain. Secondary bacterial infection is common. Lymphadenopathy is variable, but usually is mild unless secondary bacterial infection is severe. Scarring is seen with chronicity. Moderately to severely affected dogs are lame.
The syndrome is seen primarily in German Shepherd Dogs; a small number of German Shepherd Dog crossbreeds also have been seen. Some reports suggest a marked predilection for male dogs (Kristensen, 1997; Scott et al., 2001). This suggestion is intriguing, as male dogs usually are heavier and taller, supporting the theory given above regarding increased strain on soft tissue of the distal extremities. Dogs with more direct German ancestry may be over-represented (Scott et al., 2001). Adult dogs between the ages of 2 and 8 years predominate (Scott et al., 2001).
Clinically, this syndrome is quite distinctive; differential diagnosis is not problematic. Fistulous tracts initiated by foreign bodies should be considered; however, sites dorsal to the pawpads, particularly the large tarsal pads, would be atypical for foreign body penetration.
Biopsy site selection
Specimen collection is difficult since the tissue needed is the deep dermis and subcutis directly dorsal to a pawpad. Wedge technique performed under general anesthesia is recommended, since local anesthesia is difficult in this location and hemostasis may be problematic. At least part of the fistula should be included in the specimen. If multiple biopsy specimens are taken, they should be acquired from the same paw to minimize postbiopsy lameness.
Histopathology
The epidermis is moderately to severely acanthotic. If the specimen is obtained from the edge of the fistula, there is a focal area of severe ulceration. The panniculus is severely inflamed. Inflammation also may extend through the overlying dermis along one edge of the specimen, if the specimen is obtained from the edge of a fistula. In other specimens, the dermis may be relatively uninflamed and overlie cavitation and inflammation of the panniculus. In earlier lesions, neutrophils and macrophages predominate, and discrete pyogranulomas may be observed. In the more commonly received advanced lesions there are diffuse infiltrations of neutrophils, macrophages, plasma cells, and lymphocytes. Inflammation grades into areas of variable peripheral fibrosis, depending on the stage. Fibrosis is generally striking and deep, and often is most severe just beyond the most intense region of inflammation. Fibrous tissue emanates into adjacent areas, where it is accompanied by milder chronic inflammation consisting primarily of plasma cells.
Differential diagnosis based on histopathology alone is problematic, as the microscopic lesions of metatarsal fistulation are not distinctive. Any foreign body reaction or puncture-induced traumatic lesion that extends to the panniculus may appear similar, as may deep bacterial or fungal infections. Special stains for infectious agents may be required. Knowledge of the breed and site affected are key to the definitive diagnosis of this syndrome.