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Q1: What is the differential diagnosis for this patient?
Craniopharyngioma; this is the most common tumour in the region of the hypothalamus and the pituitary in this age, presenting with headache, vision impairment, various degrees of hyperprolactinaemia, and pituitary insufficiency. Two thirds of craniopharyngiomas are suprasellar and one third extend into or are within the sella.1 The majority of craniopharyngiomas are cystic or mixed cystic/solid lesions. Calcifications of the rim of the tumour mass are a common feature.
Pituitary adenoma; this was probably non-functioning (NFPA) as no signs of growth hormone excess were present and there was only a mild increase in prolactin levels. These usually present as space occupying lesions. The clinical manifestations of NFPA include headaches, visual fields defects, and extraocular nerve palsies. Pituitary insufficiency commonly results from destruction of the remaining normal pituitary tissue.
Primary hypophysitis; this is a rare disorder with about 140 cases reported worldwide.2 The clinical presentation includes headache and visual impairment as well as nausea and occasionally signs of meningitis. It usually occurs at an older age than our patient and frequently coexists with systemic disorders.
The patient underwent trans-sphenoidal surgery and complete removal of the lesion was achieved. A thin film of normal looking anterior lobe of the pituitary was identified and preserved. On microscopic examination moderately intense mononuclear inflammation, with lymphocytes, macrophages and plasma cells was found, features consistent with lymphocytic hypophysitis.
Q2: Which specific work-up should the follow up include?
As lymphocytic hypophysitis usually coexists with other autoimmune disorders,2 laboratory examination for a possible coexistence of other autoimmune disorders should be performed. In this case it was negative, including antithyroid and antinuclear antibodies; only the titre of anticardiolipin antibodies was slightly increased. Pituitary function tests should also be performed. These include thyroid function tests and prolactin levels as well as dynamic assessment of pituitary function including insulin tolerance test to assess the growth hormone and cortisol responses as well as luteinising hormone releasing hormone and thyrotrophin releasing hormone test to assess the gonadotrophin and thyroid stimulating hormone reserve. Cortisol response could also be assessed using the short Synacthen test instead of the insulin tolerance test. Plasma and urine osmolality should also be checked. The tests should be repeated after six months and yearly thereafter. Magnetic resonance imaging (MRI) of the pituitary should also be repeated at the same time points.
MRI after surgery was normal and there were no visual field abnormalities. Pituitary function tests were normal. Follow up after three years has been excellent; the menses were regular and there was no evidence of pituitary insufficiency and/or disease recurrence.
Three distinct clinicopathological entities of primary hypophysitis have been described. These are—in decreasing order of occurrence—lymphocytic hypophysitis, granulomatous hypophysitis, and xanthomatous hypophysitis.
Lymphocytic hypophysitis is encountered predominantly in women in the third and fourth decade of life, during late pregnancy, or early postpartum. It may present with headache and visual impairment. Hypopituitarism is present in 60% to 70% of cases. In 95% of cases MRI shows a solid homogeneous pituitary mass and occasionally suprasellar extension. Further radiological features of lymphocytic hypophysitis include loss of the bright spot in the posterior pituitary and thickening of the pituitary stalk. Although the aetiology of lymphocytic hypophysitis remains unknown there is evidence of an autoimmune origin as well as an association with other autoimmune disorders.2 Of the latter the most common is lymphocytic thyroiditis.
Granulomatous hypophysitis accounts for fewer than 1% of cases of all pituitary disorders and is equally distributed between the sexes (usually women are in the third decade while men are in the fifth decade of life). It can either be an isolated lesion or part of a systemic disease, such as sarcoidosis. On imaging granulomatous hypophysitis presents with mixed solid and cystic features.
Xanthomatous hypophysitis is the least common form of hypophysitis. It does not show any sex predominance and on imaging studies appears cystic.
Our patient, being an adolescent, is younger than the typical patient with lymphocytic hypophysitis, since few cases in children and adolescents have been reported.3,4 Moreover, her disease was not linked to pregnancy. Additionally, on MRI the pituitary lesion appeared cystic, a feature encountered in granulomatous hypophysitis, xanthomatous hypophysitis, and craniopharyngioma but uncommon in lymphocytic hypophysitis.
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