Hypophysitis due to IgG4-related disease responding to treatment with azathioprine: an alternative to corticosteroid therapy

Fifteen cases of lymphocytic hypophysitis due to IgG4-related disease have been reported demonstrating marked improvement with corticosteroid therapy. This is the first case of IgG4-related hypophysitis demonstrating improvement with azathioprine, where corticosteroids were initially tried but ceased due to concern regarding enlargement of the pituitary infiltrate. Case description and review of 15 cases reported in the literature. A 40 year old male was diagnosed with IgG-4 related disease based on pituitary and lacrimal gland biopsies associated with raised serum concentration of IgG4. The patient was commenced on prednisolone 30 mg/day, as rapid response to prednisolone treatment has been described in the literature for other cases of IgG4-related hypophysitis. Over the next 3 months, prednisolone treatment resulted in a reduction of serum IgG4 levels, but repeat MRI scan showed an enlarging pituitary mass with new optic nerve compression. Azathioprine 75 mg twice daily was commenced and in the subsequent 3 months, IgG4 levels normalised (0.58 g/L) and MRI scan showed 50 % shrinkage of the pituitary mass. After 10 months of azathioprine treatment the MRI showed a normal sized pituitary but persistence of the infraorbital nerve thickening. Hypophysitis due to IgG4-related disease usually demonstrates prompt response to corticosteroids. This case highlights the need to image promptly after starting treatment to exclude an enlarging pituitary mass despite corticosteroid treatment. Alternative therapy with azathioprine can result in marked improvement. It should be remembered that IgG-4 related hypophysitis is part of a multi-organ disease.