Diagnosis of autoimmune skin disease in the dog: Correlation between histopathologic, direct immunofluorescent and clinical findings

Abstract

Histopathologic, immunopathologic and clinical evaluation of two hundred thirty dogs resulted in a diagnosis of canine autoimmune skin disease (AISD) in eighty four of the suspected cases. Pemphigus foliaceus was the most common diagnosis, followed by bullous pemphigoid and pemphigus vulgaris. The highest percentage of cases were mixed breeds, followed by shelties, collies, German shepherds and poodles. There was no apparent age or sex predilection. Eighty seven percent of the eighty four cases of AISD were diagnosed on the basis of supportive clinical criteria in addition to compatible histopathologic and/or direct immunofluorescent findings. Thirteen percent of the cases with a final clinical diagnosis of AISD lacked supportive immunohistopathologic criteria on biopsy and the diagnosis was based upon clinical appearance, exclusion of other dermatoses, and response to immunosuppressive therapy. This latter group included four cases of SLE diagnosed using a combination of clinical criteria and a positive test for antinuclear antibody. Thirty three percent of the AISD cases were diagnosed on the basis of compatible findings on both histopathology and direct immunofluorescence. A histopathologic diagnosis of AISD was made in sixty nine percent of the cases. Positive direct immunofluorescence was found in fifty two percent of the cases. Thirty five percent of the AISD cases were diagnosed on histopathologic criteria without supportive immunofluorescent findings, while nineteen percent had positive direct immunofluorescence with nonspecific histopathologic changes. The number of definitive positive results was greater for direct immunofluorescence (38%) than for histopathology (25%). There was an equal incidence (21%) of false positive results among non-AISD cases with both tests. Indirect immunofluorescence appears to have little value in the diagnosis of canine AISD. The recommended diagnostic approach to canine AISD involves the use of both histopathologic and immunopathologic evaluations.