Histopathological differences between canine idiopathic sebaceous adenitis and canine leishmaniosis with sebaceous adenitis

Abstract

Sebaceous adenitis (SA) may be idiopathic (ISA) or associated with other disorders. The purpose of the present study was to compare the cutaneous histopathology of SA in cases in which Leishmania organisms were detected by immunohistochemistry (IHC) with that of cases diagnosed as ISA. Skin sections of 29 patients were evaluated histologically and divided into two groups, one characterized by several epidermal and subepidermal lesions, a granulomatous to pyogranulomatous nodular to diffuse dermatitis involving the sebaceous glands and a positive IHC for Leishmania spp. The other group was characterized by orthokeratotic hyperkeratosis, follicular keratosis with different degrees of pyogranulomatous to granulomatous SA, lack of nodular dermatitis and a negative IHC for Leishmania spp. Hidradenitis was present in both groups. From these results it can be concluded that SA in canine Leishmaniosis (CL) is usually present together with a nodular to diffuse dermal infiltrate and epidermal and subepidermal lesions, and that SA in the absence of dermal inflammation is probably not associated with or suggestive of CL, even in regions where the disease is endemic.

Cutaneous involvement in canine leishmaniosis due to Leishmania infantum (syn. L.chagasi)

“…In a recent study, sebaceous adenitis was present in half of the skin biopsies obtained from areas with exfoliative dermatitis . It is similar to the Vizsla phenotype of idiopathic sebaceous adenitis; however, in CanL sebaceous adenitis is regularly accompanied by additional findings that are not present in idiopathic sebaceous adenitis (granulomatous to pyogranulomatous nodular dermatitis in the interfollicular dermis), and follicular keratosis is milder and usually not accompanied by a dilated follicular infundibulum …”

Pathologic Mechanisms Underlying the Clinical Findings in Canine Leishmaniosis due to Leishmaniainfantum/chagasi

“…64,90,91 Within the inflammatory infiltrate, the predominating macrophages can be epithelial, vacuolated, or apoptotic. 11,148 Typical cutaneous microscopic lesions are consistent with orthokeratotic or parakeratotic hyperkeratosis, acanthosis, crusting, and ulceration in the epidermis and with inflammation of the dermis and occasionally panniculus, appearing in various histologic patterns (eg, interstitial, lichenoid, nodal, diffuse, periadnexal). 45,74 The periadnexal pattern in particular can be confused with the granulomatous form of idiopathic sebaceous adenitis.…”

“…63 However, the observation of sebaceous adenitis in clinically suspicious CanL cases (eg, exfoliative dermatitis), which is not escorted by dermal inflammation, makes the diagnosis of CanL far less possible, even in the areas where the disease is endemic. 11,107 Cutaneous ulcers that have been attributed to local trauma and/or vasculitis are usually localized on the ear margins, pressure points, limbs, and mucocutaneous junctions. 73,74 The focal or multifocal nodular form, characterized by severe granulomatous dermatitis and a high amastigote number, may indicate either inefficient or strong cellular immunity by the host.…”

A retrospective study comparing histopathological and immunopathological features of nasal planum dermatitis in 20 dogs with discoid lupus erythematosus or leishmaniosis

“…In the authors’ experience, CanL nasal planum dermatitis can be associated with a lichenoid dermatitis with or without an interface dermatitis. Lichenoid and interface dermatitis can be typical for non‐nasal skin samples from dogs with CanL and in these cases, in endemic areas, immunohistochemistry (IHC) or PCR testing is recommended to rule out the presence of Leishmania organisms in lesional skin . Macrophages, lymphocytes and plasma cells are commonly observed in the inflammatory infiltrate in both CanL and DLE, and thus differentiation of the two conditions based on the predominant inflammatory cell type is not usually feasible .…”

“…Macrophages, lymphocytes and plasma cells are commonly observed in the inflammatory infiltrate in both CanL and DLE, and thus differentiation of the two conditions based on the predominant inflammatory cell type is not usually feasible . It has been proposed that there may be differences in the composition and possibly the distribution of the mononuclear cell infiltrate between DLE and CanL …”