Paraneoplastic syndromes - emergency medicine perspective
Introduction
Paraneoplastic syndromes (PNS) are clinical disorders caused by substances (hormones, cytokines, peptide factors) produced by a tumour, or by immune responses to tumour antigens that cross‑react with normal tissues.
They produce systemic or remote organ dysfunction that is not due to direct tumour invasion, metastasis, infection or treatment toxicity.
In emergency care, PNS are important because they may be the first sign of an occult malignancy, can cause life‑threatening biochemical or neurological derangements, and demand early recognition, directed investigation and specialist referral (oncology, neurology, endocrinology).
This section summarises practical, ED‑relevant recognition, initial management and disposition and aligns with UK guidance on suspected cancer and emergency biochemical problems (NICE NG12, NICE NG127; RCEM / Society for Endocrinology hypercalcaemia guidance; NICE CG174).
Pathophysiology
- Ectopic hormone production: tumours (classically small‑cell lung cancer and neuroendocrine tumours) may secrete ACTH, ADH, PTHrP, serotonin and other bioactive substances producing endocrine syndromes.
- Immune‑mediated cross‑reactivity: tumour antigens induce autoantibodies or T‑cell responses that damage neural or other tissues (common in paraneoplastic neurological syndromes).
- Cytokine/metabolic and remote trophic effects: cytokine release, ectopic erythropoietin or growth factor effects cause constitutional symptoms, erythrocytosis, hypertrophic osteoarthropathy and other manifestations.
Epidemiology and tumour associations
PNS are relatively uncommon but clinically meaningful - reported in roughly 10-20% of people with cancer, varying by syndrome and tumour type.