IgG4-related hypophysitis

IgG4-related hypophysitis is a rare cause of inflammation of the pituitary gland and an uncommon manifestation of the systemic IgG4-related disease (IgG4-RD).

Epidemiology

Although IgG4-RD tends to present in middle-aged and elderly men, the gender ratio is more balanced in patients with IgG4-related hypophysitis and other head and neck manifestastions of IgG4-RD .

Clinical presentation

Clinical features depend on the part of the pituitary gland involved :

• adenohypophysitis (anterior pituitary involvement): 
  • hypopituitarism or individual endocrine hormone deficiencies (e.g. hypothyroidism, hypogonadism)
  • mass effects on adjacent structures (e.g. optic chiasm)
• infundibuloneurohypophysitis (posterior pituitary involvement): diabetes insipidus
• panhypophysitis (both anterior and posterior pituitary involvement): all of the above clinical features

Pathology

IgG4-related hypophysitis is characterized by chronic inflammation of the pituitary gland with histology revealing lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells . This classic histological finding differentiates it from the histological appearances of other etiologies of hypophysitis, those being:

• lymphocytic hypophysitis: lacks plasma cells and presents in a young female demographic
• granulomatous hypophysitis: has multinucleated giant cells that form true granulomas, is secondary to diseases such as neurosarcoidosis, and also tends to present in a young female demographic
• xanthomatous hypophysitis: has foamy histiocytes (xanthoma cells) and macrophages
• necrotizing hypophysitis: extremely rare and has necrosis with only scattered pituitary tissue remaining

Radiographic features

Although this is a very rare entity, common radiographic findings that have been reported include non-specific enlargement of the pituitary gland with or without infundibulum enlargement that is visible on both CT and MRI . Post-contrast T1-weighted MR images may further reveal enhancement .

Other associated head and neck manifestations of IgG4-RD, such as IgG4-related hypertrophic pachymeningitis, may also be seen .

Treatment and prognosis

Based on case series-level evidence, good response is seen to corticosteroids such as prednisolone or hydrocortisone . Treatment of endocrine hormone deficiencies (e.g. giving desmopressin for diabetes insipidus) is also prudent .

Differential diagnosis

The differential diagnosis is primarily that of other pituitary region masses. Considerations include:

• pituitary adenoma
• craniopharyngioma (papillary type)
• suprasellar meningioma
• pituitary metastasis
• lymphocytic hypophysitis
• granulomatous hypophysitis (e.g. due to neurosarcoidosis)
• xanthomatous hypophysitis
• necrotizing hypophysitis