Intrachiasmatic abscess caused by IgG4-related hypophysitis
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Autoimmune hypophysitis is a rare disease of the pituitary, which may affect vision by inflammation and compression of the optic chiasm. However, intrachiasmatic abscess formation has not been previously reported.
In this study, we report a case of a 29-year-old female with bitemporal hemianopia due to a cystic intrasellar tumor. The patient underwent surgical decompression of the lesion, which was found to be an intrachiasmatic abscess.
The histologic findings were consistent with IgG4 hypophysitis.
This rare clinical presentation suggests that in case of a disproportionate degree of visual impairment in relation to the size of the lesion, suspicion should lead to an intrachiasmatic lesion.
KeywordsAbscess Hypophysitis IgG4 Intrachiasmatic
Hypophysitis is an infiltrative disease of the pituitary gland, with a predilection in women, especially in the postpartum period [3, 9]. Primary hypophysitis is usually classified as lymphocytic, granulomatous or xanthomatous, based on the histologic characteristics. However, rare variants of primary hypophysitis have recently been established such as IgG4-related hypophysitis and necrotizing hypophysitis . The pathogenesis is probably autoimmune, but with different pathologic features of the lymphocytic, granulomatous, xanthomatous, IgG4-related or necrotizing hypophysitis . Lymphocytic adenohypophysitis is mediated by anti-pituitary antibodies against pituitary antigens exposed by the enlarged gland during pregnancy, combined with postpartum autoimmune exacerbation . Magnetic resonance imaging (MRI) findings suggestive of hypophysitis include symmetric enlargement of the pituitary gland, a thickened stalk, a usually intact sellar floor and homogeneity of the pituitary mass, which enhance after gadolinium. Diffuse infiltration of the pituitary gland by inflammatory cells results in varying degrees of endocrine dysfunction, including diabetes insipidus. Other clinical manifestations of the disease include headache, general weakness and visual disturbance . Primary hypophysitis is rare and has a tendency to recur. We report an intrachiasmatic abscess as a manifestation of recurrent Ig4-related hypophysitis in a 29-year-old female. There are to our knowledge no previous reports of any type of intrachiasmatic abscess.
Postoperatively, the patient complained of minor headaches and dizziness. The microbiologic examination for bacteria and fungi was negative. Blood analysis showed an elevated IgG4 (>135 mg/dl). The quantiferon test for tuberculosis and all the markers for rheumatic diseases (ACE, ANA, ANCA) were negative. The original biopsy showed adenohypophysis with a severe, diffuse, mixed inflammatory infiltrate, including T-cells, B-cells, plasma cells, neutrophil and eosinophil granulocytes and histiocytic cells. Special stains for TB (Ziehl-Nielsen) and fungi (PAS and Gomori-Trichrome) were negative. No bacterial infiltrates were found. The biopsy was re-evaluated at the time of the second operation, and immunostains for IgG4 and IgG were performed. The IgG4 staining showed areas with more than ten IgG4-positive plasma cells per ten high power fields, and based on this finding, it was concluded that the criteria for IgG4-related disease were fulfilled.
The clinical presentations of primary hypophysitis are variable, ranging from hypopituitarism and diabetes insipidus to visual impairment, cranial nerve palsies and headache. Headache is considered the result of distortion of the dura and diaphragma sellae by the expanding sellar mass. Visual abnormalities include visual field defects, classically bitemporal hemianopia, decreased visual acuity and dyschromatopsia secondary to compression of the chiasm and the optic nerves by the expanding pituitary mass. Partial or complete suppression of the anterior pituitary hormones produces the classic signs of hypoadrenalism, hypothyroidism and hypogonadism. Diabetes insipidus is due to a lack of ADH, attributed to direct immune destruction of the posterior lobe .
Diagnosis of hypophysitis based on MRI findings can be quite challenging. However, the symmetry of pituitary enhancement, lack of erosive changes of the sellar floor and intense enhancement of the pituitary gland after gadolinium can be diagnostic in the proper clinical background [3, 12].
Despite typical clinical and imaging findings, some primary hypophysitis cases may still go undiagnosed or require a long-term treatment. In our case, the management of the relapse and final treatment of the patient lasted more than 5 months. Initially the cystic tumor was small and close to the optic chiasm, but did not compress the optic pathways. An inflammatory activity in the cystic process (hypophysitis reactivation) with a secondary inflammatory activity in the chiasm was suspected to give rise to the visual disturbances, which is why she was initially treated with steroids. However, the last MRI revealed a cystic intrachiasmatic formation, which led to further worsening of the visual fields and required surgical intervention. This manifestation of the hypophysitis must be extremely rare. Direct invasion of the chiasm by the inflammatory process is our best explanation for the development of the intrachiasmatic abscess.
IgG4-related hypophysitis is characterized by an abundance of IgG4-producing plasma cells and was first reported in 2004 . Since then, several cases have been reported, and the diagnosis is presumably underestimated [1, 2, 5, 6, 7]. This case demonstrates a new presentation of IgG4-related hypophysitis. To the best of our knowledge, no previous case of an intrachiasmatic abscess caused by IgG4-related hypophysitis has been described.
Hypophysitis is a rare but increasingly recognized pituitary disorder. The entirely intrachiasmatic relapse of the disease in our case has not previously been reported, but should be considered when a mismatch between the size of a structural lesion and the degree of visual impairment occurs. In addition, the intrachiasmatic abscess adds a new presentation of IgG4 hypophysitis.
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All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
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