We present a case of a 25-year-old male with no significant past medical history presenting with extensive bilateral cervical lymphadenopathy, thirst and polyuria. He denied night sweats, weight loss or a change in appetite. There was no reported previous contact with tuberculosis and he had not travelled to high risk areas. A water deprivation test was consistent with a diagnosis of diabetes insipidus.
Computerised Tomography scanning of the chest demonstrated extensive lymphadenopathy throughout the neck, chest and abdomen in addition to patchy change in the right lung apex. Cervical lymph node biopsy showed caseating ganuloma. Ziehl-Neelsen stain was negative but unfortunately samples were not sent for culture for Mycobacterium tuberculosis at the time of biopsy. Assessment of anterior pituitary function was normal as was pituitary imaging using magnetic resonance imaging.
The patient went on to have a bronchoscopy which was unremarkable. Upper lobe bronchial biopsy samples have shown no evidence of granulomatous change with no acid-fast bacilli seen on auramine staining. Results from lavage samples as well as Quantiferon-TB GOLD are awaited. Original lymph node samples have been sent for PCR for tuberculosis. The patient is likely to require further lymph node biopsy in order to obtain samples for culture.
Whilst it is clear that this patient has cranial diabetes insipidus, we are still challenged as to what the primary cause is. Cranial diabetes insipidus due to sarcoidosis is rare; that due to tuberculosis without TB meningitis is extremely rare. Caseating granuloma is classical but not exclusive for tuberculosis. Treating the patient with both steroids and tuberculosis drugs could prove to be extremely problematic should he go on to develop complications of treatment such as hepatitis. This presents us with a challenge as how best to proceed.