Adenohypophysitis associated with sebaceous gland atrophy in a dog.

Sebaceo us adeniti s is a granulomatous or pyogranul ornatous dermatitis with inflammation located around sebaceous glands. In chronic cases, these gland s are replaced by fibrous connective tissue} Many breeds of dogs have been affected , but adult Standa rd Poodles, Sam oyeds, Vizlas, and Akitas are appare ntly predisposed.' Etiologic facto rs are unknown. Seconda ry pyoderma is often a complicati ng factor. Sebaceous aden itis should be considered in the different ial diagnosis of dogs with seborrhea sicca that is unresponsive to medic al therap y.' A 9-year-old, castrated male Samoyed dog was euthanatized and presented to the Colorado Stat e University Veterinary Teaching Hospital for necropsy. It had a 3-year history of a generalized derm at itis and blepharitis that was unresponsive to conventional medical therapy. Serologic and endocrine function tests were never performed. Th e entire hair coat was thin, and the skin was rough, dry, and scaly. Th ere was partial alopecia and crusting of the eyelids . Th e externa l ear canal s were dirty and scaly. A postmort em examination of the abdomen, thorax, and brain revca led no other gross lesions. Th e tissues that were examined histologically were multiple areas of trun cal skin, external auditory canal, upper and lower eyelids, nictitating membrane, th yroid , adrenal, hypophysis, and both eyes. Sebaceo us gland s were absent in all areas ofskin examined. Dorsal thoracic and dorsal lumbar skin had mild to moderate epidermal and follicular orthoke ratotic hyperkeratosis and moderate infiltrat ion aro und hair follicles by lymph ocytes and plasma cells (Fig. I). Ove r 150 sections from one sample of skin were cut and examined. No sebaceo us glands were found in any section. Focal areas of epidermis were mi ldly acanthotic, varying from two to five cell layers thi ck. Sma ll numbers of lymphocytes and plasma cells were scatt ered in the papillary derm is. Hair follicles were in catagen and anagen phases. Apocrine sweat glands were moderately dilated and were often surro unded by a Iymp hoplasmacytic infiltra te. Changes in ventral thoracic skin were simi lar but less pronoun ced. Hair follicles in an externa l auditory canal were hyperkeratotic. Ceruminous glands and hair follicles were surro unded by lymphocytes and lesser numbers of macroph ages, fibroblasts , and a few neutrophils. As in the skin , sebaceous glands were absent. Epith elium of an upp er eyelid was acanthotic and had parakerat otic hyperkeratosis. A superficial crust consisted of keratin debris and neut roph ils. Hair follicles were plugged with kera tin and often con tained neutrophils. Heavy infiltrations of lymphocytes, plasma cells, and macrophages surrounded hair follicles and the tubul ar gland s of Moll. Tarsal glands , which are modified sebaceous glands, were absent. Th e nictit at ing membrane contained a normal am ount of tubular lacrimal gland s with sma ll interstitial accumulations of plasma cells. Th ere were dense accumulatio ns of plasma cells in the subconjunctiva. The zona fasciculata and zona reticularis of an ad renal gland were j udged subjective ly to be thickened in relation to the zona glomeru losa and the medu lla. Examination of thyroid gland revealed no microscop ic abnormalities. Th e eyes had no microscopic lesions. In the adenohypophysis, multiple, large foci contained a Iymph oplasmacytic infiltrate and scattere d cells that were either chro mophobic pitu itary cells, which they closely resembled, or macroph ages. Th ese cells had vesicular , sometim es indented nuclei, and indi stin ct cytoplasm. Acidophilic and basophilic cells were greatly decreased or absent in the inflam ed areas (Fig. 2). Th ere was a pale, eosinophilic, loose, fibrillar matrix in affected foci. A Masson 's trichrome-stained sectio n failed to reveal an increase d amo unt ofcollagen. The neurohypoph ysis was not affected. Sebaceo us glands are normally present in all regions of haired skin.' Th e history, signalment, distribution of skin lesions , and absence of sebaceous gland s in thi s case are compatible with chronic or end-s tage sebaceous adenitis of dogs.'> In contrast to those cases of sebaceous adeniti s previously described in the literatu re, the dermatitis in thi s dog was not granulomato us. It is possible that the leukocytic infiltrate was modified as the sebaceo us glands disapp eared. It is also possible that thi s case represent s a non-granulomatous variant of the disease syndrome.