Adenohypophysitis associated with sebaceous gland atrophy in a dog

Presence of CD3+ and CD79a+ Lymphocytes in the Pituitary Gland of Dogs at Post-mortem Examination

Hypophysitis has been reported occasionally in dogs, with most cases resembling primary lymphocytic hypophysitis in man. Although it is generally assumed that lymphocytes are not present normally in the canine pituitary gland, few studies have investigated this hypothesis. However, lymphocytes are recognized in the pituitary gland of people and horses without signs of pituitary disease. It is unknown to what degree lymphocyte infiltration of the pituitary gland might occur as an incidental finding in dogs. The aim of the present study was to investigate the presence and distribution of lymphocytes in the pituitary gland of dogs without clinical suspicion of pituitary disease. Twenty dogs were subjected to routine necropsy examination. Formalin-fixed and paraffin wax-embedded sections of pituitary were stained with haematoxylin and eosin (HE) or subjected to immunohistochemistry (IHC) using primary antibodies specific for the T-cell marker CD3 and the B-cell marker CD79a. The number of CD3⁺ and CD79a⁺ cells per area unit (CPA) was determined for different pituitary regions. Two dogs had extensive neoplastic lesions in the pituitary gland and were excluded from analysis. In the remaining 18 dogs, occasional scattered CD3⁺ cells were found in the pituitary gland. There was a significant difference in CD3⁺ CPA between pituitary regions (P = 0.001). The highest CD3⁺ CPA was found in the pars tuberalis (median 41.3 cells/mm², interquartile range 20.9-50.5 cells/mm²). In six of the 18 dogs (33%), CD79a⁺ cells were detected in small number (median total cell number 0 cells/section, interquartile range 0-1.0 cells/section). This study shows that T cell, and fewer B cells, may be found in the pituitary gland of dogs without clinical suspicion of pituitary disease. Regional difference in T-cell density, with the highest CD3⁺ CPA in the pars tuberalis, may imply regional immunoregulatory functions in the canine pituitary gland.

Pathological Findings in the Pituitary Glands of Dogs and Cats

With the exception of classic functional adenomas in dogs and horses, pituitary lesions are infrequently described in the veterinary literature. Approximately 10% of pituitary glands from asymptomatic humans contain abnormalities, but the equivalent proportion in small animals is unknown. Pituitary glands from 136 dogs and 65 cats collected during routine necropsies were examined to determine the prevalence of pituitary lesions and their histopathological diagnosis. Lesions were characterized in sections stained with hematoxylin and eosin, periodic acid-Schiff (PAS), Gordon and Sweet’s and reticulin stains, and immunohistochemistry for adrenocorticotropic hormone (ACTH), growth hormone, melanocyte stimulating hormone–α, and prolactin. Pituitary abnormalities were identified in 36 of 136 (26.4%) dogs and 10 of 65 (15.3%) cats. Cystic changes were the most common lesion, occurring in 18 (13.2%) dogs and 8 (12.3%) cats. Pituitary neoplasia was detected in 14.1% (12/85) of middle-aged and old dogs; 1 (1.5%) cat had pituitary nodular hyperplasia. PAS and reticulin stains helped differentiate ACTH-immunoreactive adenomas from hyperplastic nodules: adenomas contained PAS-positive intracytoplasmic granules and loss of the normal reticulin network. One dog had a pituitary carcinoma with infiltration into the thalamus. Other pituitary abnormalities included secondary metastases (2 dogs) and hypophysitis (4 dogs, 1 cat). In most cases, the lesion appeared to be subclinical and could be considered incidental, whereas clinical manifestations were apparent in only 4 dogs (2.9%) and none of the cats with pituitary lesions. Pituitary abnormalities are common in dogs and cats, and their clinical relevance requires further investigation.

Hypophysitis, Panhypopituitarism, and Hypothalamitis in a Scottish Terrier Dog

A 6‐year old male neutered Scottish Terrier was referred with a 1 week history of progressive lethargy and anorexia. Neurological examination localized a lesion to the forebrain and hormonal testing showed panhypopituitarism. Magnetic resonance imaging (MRI) of the brain revealed a rounded, well‐defined, suprasellar central mass. The mass was slightly hyperintense to the cortical grey matter on T2‐weighted (T2W), hypointense on T1‐weighted (T1W) images and without T2* signal void. There was a central fusiform enhancement of the mass after contrast administration which raised the suspicion of a pituitary neoplasm. Rapid deterioration of the dog prevented further clinical investigations. Histopathologic examination revealed a lymphocytic panhypophysitis of unknown origin suspected autoimmune involving the hypothalamus (hypothalamitis). This is a unique case report of a dog presenting with inflammatory hypophysitis and hypothalamitis of suspected autoimmune origin with detailed clinical, MRI, histology and immunohistochemistry findings.

Restored vision in a young dog following corticosteroid treatment of presumptive hypophysitis

Background

Hypophysitis is an umbrella term for a group of disorders involving inflammation of the pituitary gland. A rare occurrence in humans, hypophysitis can produce a range of clinical signs including (but not limited to) visual deficits and diabetes insipidus. Only five cases of canine hypophysitis exist in the literature, all presenting in mature dogs with no visual deficits and a grave outcome. This case report describes the clinical and advanced imaging features of blindness-inducing presumptive hypophysitis in a dog, which rapidly resolved with medical management.

Case presentation

A 1-year-and-seven-month-old neutered male Standard Poodle presented with subacute blindness, ataxia, and polyuria/polydipsia (PUPD). Magnetic resonance imaging (MRI) detected a contrast-enhancing pituitary mass with perilesional oedema compromising the optic chiasm. Suspecting neoplasia, anti-inflammatory corticosteroid was commenced prior to radiation therapy planning. Complete resolution of neurological and visual deficits occurred within 12 days of starting steroid treatment. Repeated advanced imaging indicated macroscopic resolution of the lesion. An extended thyroid panel with insulin-like growth factor-1 analysis supported a diagnosis of hypophysitis. Resolution of PUPD was achieved with tapering courses of prednisolone and desmopressin; the dog has since been clinically normal for 14 months and treatment-free for 11 months.

Conclusions

To the authors’ knowledge, this is the first instance in which a canine pituitary mass has demonstrated long-term resolution with palliative medical treatment alone, alongside reversal of associated blindness and presumptive diabetes insipidus. We suspect this lesion to be a form of hypophysitis, which should be included among differential diagnoses for pituitary masses, and for subacute blindness in dogs. Where possible, we advocate biopsy-confirmation of hypophysitis prior to timely intervention with anti-inflammatory treatment.

Occurrence of primary lymphocytic hypophysitis in two horses and presence of scattered T-lymphocytes in the normal equine pituitary gland

The postmortem examination of a 14-y-old Appaloosa gelding with clinically diagnosed pituitary pars intermedia dysfunction showed a unique finding of moderate multifocal lymphocytic hypophysitis (LH). The pituitary glands of 24 horses submitted for postmortem examination were examined grossly and examined histologically for the presence of lymphocytes. Of these 23 horses, 1 additional case suffered from moderate LH. The 2 cases with LH tested negative for Equid herpesvirus 1 and 4 by polymerase chain reaction and immunohistochemistry (IHC), and no viral particles were observed by electron microscopy in 1 case examined. The cause of LH remains unknown, but based on the T-lymphocytic nature of the inflammation and the human literature, an immune-mediated origin is hypothesized. In addition, the review of 24 cases revealed that 10 horses had few and small multifocal lymphocytic infiltrates within the pituitary gland; the remaining 12 horses showed no evident lymphocytes when examined by hematoxylin and eosin. IHC for CD3 showed the presence of a small number of individual T-lymphocytes scattered through the gland in all examined horses, which appears therefore to be a normal feature of the pituitary gland in horses.

Lymphocytic Adenohypophysitis and Adrenalitis in a Dog With Adrenal and Thyroid Atrophy

A 4.5-year-old spayed female Great Pyrenees with hypothyroidism and hypoadrenocorticism had a slightly enlarged pituitary gland and bilaterally atrophic adrenal and thyroid glands. Lymphocytic adenohypophysitis and adrenalitis were found in which B lymphocytes and plasma cells dominated the adenohypophysitis but T cells dominated the adrenalitis. The thyroid gland had extensive follicular atrophy and collapse. The combination of primary hypothyroidism and hypoadrenocorticism resembles type II autoimmune polyendocrine syndrome or Schmidt syndrome in humans. Adenohypophysitis is rare in dogs and not reported in polyendocrine disease in animals.

Sebaceous adenitis in the Akita: clinical observations, histopathology and heredity

Ninety-seven pure-bred Akitas were examined clinically and histologically for sebaceous adenitis. The diagnosis was established histologically in 23 Akitas by demonstrating an inflammatory reaction targeted against the sebaceous glands or a reduction in the number of glands. The clinical course of sebaceous adenitis in the Akita was similar to that seen in other breeds. The first skin lesions occurred mainly on the dorsal midline and ears. Compared with the Poodle, the age at first onset of the disease was more variable and the hair loss affected mainly the undercoat. The progression of sebaceous gland destruction varied between dogs and was not seen in all cases. Because bud-like sebaceous gland proliferation could be identified, it seems that regeneration of the sebaceous glands may occur. An autosomal recessive inheritance appears to be possible. Apart from a genetic background, immune-mediated factors possibly influence the onset and course of sebaceous adenitis.