Pustular dermatitis in dogs affected by leishmaniosis: 22 cases

Background: Skin lesions in canine leishmaniosis (CanL) are diverse, including exfoliative, ulcerative, nodular and papular dermatitides. An uncommon pustular form has also been reported. Hypotheses/Objectives: We hypothesized that CanL infection can produce a pustular reaction pattern in the skin of dogs. The aim of this retrospective study was to describe the clinicopathological features of dogs with CanL infection and pustular dermatitis, and correlate them with response to therapy. Animals: Twenty two affected dogs. Methods: Retrospective review of medical records and examination of archived biopsy materials or previously processed glass slides was performed. Cytological examinations had been recorded for all cases. Specimens were available for histopathological examination in 17 of 22 cases and for immunohistochemical detection of Leishmania amastigotes in 13 of 22 cases. Results: All dogs presented with multifocal to diffuse pustular dermatitis. CanL was diagnosed by IFAT serology (20 cases), bone marrow cytology (one case) or bone marrow PCR (one case). Cytological and/or histopathological examinations revealed acantholytic keratinocytes within pustules in 18 of 22 cases. Bacterial and fungal cultures were not performed. Leishmania amastigotes were identified by histopathology within the dermis in three cases; immunohistochemistry was positive in four cases. All dogs underwent concurrent anti-leishmanial and immunosuppressive therapy to control the pustular dermatitis, with favourable outcome in 11 of 22 cases. Conclusions and clinical importance: Due to the retrospective nature of this study it is not possible to either accept or reject the hypothesis that CanL is the direct cause of pustular dermatitis.