Interleukin-6-producing non-secreting cervical paraganglioma presenting with fever of unknown origin and systemic inflammatory response syndrome.

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumours that usually present with symptoms related to catecholamine excess. However, a small subset may secrete cytokines such as interleukin-6 (IL-6), leading to atypical systemic manifestations and delayed recognition of a paraneoplastic inflammatory syndrome. We report the case of a middle-aged woman with a previously diagnosed non-secreting cervical paraganglioma who developed fever of unknown origin (FUO), anaemia and liver dysfunction 5 years after the initial diagnosis. Extensive investigations excluded infectious, autoimmune and haematological causes. Markedly elevated IL-6 levels suggested a paraneoplastic inflammatory syndrome. Corticosteroid therapy induced transient clinical improvement, while definitive surgical resection resulted in complete resolution of fever, normalisation of inflammatory markers and recovery of haematological and hepatic abnormalities. Histopathology confirmed IL-6 expression within tumour cells. This case highlights the importance of considering cytokine-secreting paragangliomas in patients with unexplained systemic inflammation, even in the absence of catecholamine hypersecretion.