Intravascular large B-cell lymphoma presenting with SIAD and pituitary insufficiency: a unifying diagnosis for multiple endocrinopathies.

Summary: Intravascular large B-cell lymphoma is an uncommon haematological condition that may present with a variety of non-specific symptoms and signs. In this report, we discuss the case of a man in his 70s who presented with subacute cognitive and functional decline. Subsequent investigation revealed hyponatraemia secondary to syndrome of inappropriate antidiuresis (SIAD), as well as hypopituitarism. The underlying aetiology for his condition was not discovered until postmortem examination following his death from respiratory failure, which demonstrated intravascular lymphoma involving multiple organs, including the brain, dura and pituitary. As such, this case represents the challenging diagnosis of a rare cause of multiple endocrinopathies. Learning points: Intravascular lymphoma is a rare diagnosis, often presenting with non-specific symptoms and biochemical derangements. This condition should be considered as a differential diagnosis for hypopituitarism, presenting in isolation or in combination with the syndrome of inappropriate antidiuresis. A broad and multisystem differential diagnosis should be considered for any patient presenting with endocrinopathy.