Idiopathic hypertrophic pachymeningitis mimicking prolactinoma with recurrent vision loss

Idiopathic hypertrophic pachymeningitis is a rare inflammatory condition with diffuse thickening of the dura mater, which may cause a compressive effect or vascular compromise. We report on a 28-year-old Chinese woman with a history of granulomatous mastitis 7 years previously and oligomenorrhoea, headache, blurred vision, and raised prolactin level 2 years previously, that was diagnosed as prolactinoma and treated conservatively with bromocriptine. However, she had recurrent bilateral vision loss when the bromocriptine was stopped. Her symptoms were resolved by high-dose steroid injection but remained steroid-dependent. Serial magnetic resonance imaging scan showed progressive diffuse thickening of the pachymeningitis with disappearance of pituitary apoplexy. Lumbar puncture showed lymphocytosis with no organisms. Open biopsy of the meninges was performed and histology showed features of inflammatory infiltrates and vasculitis. This is an unusual presentation of a rare condition in this age-group, with co-existing granulomatous mastitis and chronic otitis media, and is a diagnostic challenge mimicking pituitary macroadenoma and meningioma in initial magnetic resonance imaging scans.