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What Hypophysitis means +
Histo-pathological Classification +
Lesions of the pituitary gland can be broadly classified into two groups:
- neoplastic (tumors), and
- non-neoplastic (non-tumors)
The neoplastic lesions (tumors) are the most common (about 90% of the total) and among them adenomas rank number one.
Non-neoplastic lesions comprise congenital defects (such as Rathke's cleft cyst, pituitary agenesis or pituitary aplasia), circulatory disorders (such as Sheehan's syndrome), pituitary hyperplasia (mainly affecting the prolactin cells), the empty sella syndrome (a reduction in the volume of the sellar contents), and the various forms of hypophysitis.
Hypophysitis literally means inflammation of the hypophysis. It can be classified into primary and secondary (see Figure 2).
Primary hypophysitis is increasingly being recognized. The term primary means that the inflammation affects the hypophysis directly. Primary hypophysitis, from now on referred to as simply hypophysitis, is important because it mimics, clinically and radiologically, the more frequent tumors of the sellar region (especially adenomas). It's management, however, is very different. Hypophysitis can be classified according to the histology into four histological types (image on the right).
- Granulomatous hypophysitis was first described in 1917 by M. Simmonds (Virchows Archives 223: 2P81-90). He reviewed the pituitaries of 2000 autopsies and described 4 cases with a collection of multinucleated giant cells, histiocytes, variable number of lymphocytes and plasma cells, not related to tuberculosis or syphilis. Here is the scan of the first figure from Simmonds' paper.
The first case reported before death was in 1980 (Taylon, J Neurosurg 52: 584-87). The disease is rare and affects males and females equally. Its pathogenesis (how diseases develop) is unknown but likely not autoimmune. Some researchers, however, do consider granulomatous hypophysitis as part of the autoimmune hypophysitis disease spectrum.
- Xanthomatous hypophysitis is even less frequent than granulomatous hypophysitis. It was first described in 3 cases in 1998 (Folkerth, RD Am J Surg Pathol 22: 736-41). Since then only 4 additional cases have appeared in the literature: one in Cheung et al (JCEM 86: 1048-53, 2001), one in Deodhare, SS et al (Endocrine Pathology 10: 237-241, 1999), and two in Tashiro et al (Endocrine Pathology 13: 183-195, 2002). Histologically, this type of hypophysitis is characterized by foamy (lipid-rich) histiocytes with variable number of lymphocytes (type of white blood cells). Because these lesions are more likely to be cystic than the other hypophysitidies, researchers have proposed that they represent a response to a ruptured cyst.
- Nectrotizing hypophysitis is the least common form of primary hypophysitis. It has been described only once in two patients in 1993 by Ahmed et al (JCEM 76: 1499-1504). The lesion involves the adenohypophysis, the neurohypophysis, the pituitary stalk and the hypothalamus. It is characterized histologically by necrosis (tissue death) surrounded by a dense infiltration with lymphocytes, plasma cells, and a few eosinophils (type of white blood cell) and considerable fibrosis.
- Lymphocytic (or Autoimmune) hypophysitis is the most frequent type of primary hypophysitis. It is our favorite disease and the main reason we created this site.
Secondary hypophysitis is quite rare today. The term secondary, applied to hypophysitis in 1994 by Sautner et al, indicates that the inflammation is secondary to an inflammation of the nearby structures or part of a systemic disease. Therefore, secondary hypophysitis can usually be diagnosed without great difficulty. Examples of secondary hypophysitis are indicated in the table below.
|Caused by local lesions||Caused by sytemic disease|
|Rathke's cleft cyst
Meningitis ( inflammation of the meninges )
Osteomyelitis of the spheniod bone
Purulent otitis media
Langerhans cell histiocytosis
Infections (septicemias, AIDS)