Isolated pituitary granuloma by atypical Mycobacterium in a nonimmunosuppressed woman

A 32‐year‐old woman presented with a 10‐day history of fever (38·0°C), headaches, nausea, vomiting and a 6‐month history of diabetes insipidus and amenorrhoea. Two months previously she had undergone a surgical drilling of the right mastoid area because of mastoiditis. Endocrine investigation showed elevated serum prolactin levels, secondary adrenal and gonadal failure and a normal thyroid function. Cranial MRI scan revealed a contrast enhancing intrasellar mass (∼2 cm) of heterogeneous appearance with suprasellar extension and thickening of the pituitary stalk. Lumbar puncture was suggestive of aseptic meningitis. The Ziehl–Neelsen stain of cerebrospinal fluid (CSF) and the tuberculin skin test were both negative. The pituitary mass was removed with a transsphenoidal approach. Histological examination demonstrated destruction of the adenohypophysis by epithelioid granulomas with partial caseous necrosis and microabscess formation, suggestive of a mycobacterial infection. A polymerase chain reaction analysis performed on paraffin‐embedded tissue was positive for mycobacterial DNA. According to the individual 16S sequence, it was identified as Mycobacterium malmoense, an atypical nontuberculous mycobacterium (NTM). In conclusion, this is the first case of an isolated pituitary granuloma caused by an NTM infection in a nonimmunosuppressed patient.