Paediatric-onset chronic inflammatory demyelinating polyradiculopathy: epidemiology, natural history and disease mimics

<h3>Introduction</h3> Chronic inflammatory demyelinating polyradiculopathy (CIDP) typically presents in adulthood. Paediatric-onset CIDP is rare and may be difficult to distinguish from inherited/metabolic neuropathies. We aimed to study the natural history and epidemiology of the disease, and alternative diagnoses in patients with atypical features. <h3>Methods</h3> We interrogated the national intravenous immunoglobulin (IVIg) database for patients treated with IVIg for a diagnosis of CIDP ≤ 18 years between 2009–2023. 183 individuals (56% male) were identified. We present in detail fourteen individuals referred to a national neuromuscular centre, upon transition to adult services, noting initial presentation, treatment response, and final diagnosis. <h3>Results</h3> Fourteen individuals (50% male) were studied with median onset 13 years (range 1–18) and follow- up interval 15 years (range 3–39). All but the one patient who improved spontaneously had immunotherapy, including IVIg (n=12), steroids (n=8), mycophenolate/azathioprine, cyclophosphamide, plasma exchange, and rituximab (n=2–3 patients each). Eleven patients retained a CIDP diagnosis at final review (seven patients with stable disease off immunotherapy, four patients with active disease on immunotherapy). Three patients had alternative diagnoses, including Contactin-1/CASPR-1 antibody associated paranodopathy, inherited auto-inflammatory disease with heterozygous NOD2 mutation, and distal hereditary motor neuropathy with conduction block. <h3>Conclusions</h3> Paediatric-onset CIDP patients with atypical clinical features and/or lack of response to immunomodulatory treatment should have alternative diagnoses explored, including the more recently described nodo-paranodopathies, auto-inflammatory diseases, and other inherited/metabolic neuropathies.