Objective:

To define the incidence and prevalence of immune-mediated neuropathies (IMN) in Olmsted County, Minnesota

Background:

IMN are treatable yet disabling disorders, but population-based epidemiologic data remain limited.

Design/Methods:

We conducted a population-based study of Olmsted County, Minnesota residents diagnosed with IMN from January 1, 2011, through December 31, 2023, using the Rochester Epidemiology Project. Age‑ and sex‑standardized incidence and prevalence rates per 100,000 were calculated. Temporal trends were assessed annually and across two periods (2011–mid-2016 and mid-2016–2023).

Results:

We identified 134 patients (median age, 60 years; 53% male). The standardized point prevalence for all IMN on January 1, 2020, was 47.3 (95% CI, 37.2–59.3) per 100,000. The overall incidence (2011–2023) was 6.2 (95% CI, 5.2–7.5) per 100,000. Incidence was highest for diabetic radiculoplexus neuropathy (DRPN; 1.8), followed by Guillain–Barré syndrome (GBS; 1.6), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP; 0.8), and idiopathic inflammatory neuropathies (including inflammatory plexopathies, radiculoplexus neuropathies, axonal polyradiculoneuropathies, and mononeuropathies; 0.7). Lower rates were observed for biopsy–proven systemic vasculitis (0.25) and non-systemic vasculitic neuropathies (0.24). Other etiologies, including multifocal motor neuropathy, immune checkpoint inhibitor (ICI)–related neuropathies, and paraneoplastic neuropathies, were rare (≤0.16).

The incidence of IMN remained stable between 2011–2016 (6.6) and 2016–2023 (6.0). Compared with older adults (>50 years), younger adults (≤50 years) had a significantly lower incidence rate ratio (IRR, 0.14; 95% CI, 0.10–0.20; p<0.001) and prevalence rate ratio (PRR, 0.08; 95% CI, 0.04–0.14; p<0.001). The PRR was higher in males than females (1.66; 95% CI, 1.1–2.7; p=0.03). No racial differences were observed.

Conclusions:

IMN represents a substantial population burden, with higher-than-expected prevalence despite stable incidence over time. DRPN and GBS predominate, and emerging subtypes such as immune checkpoint inhibitor (ICI)–related neuropathies, highlight evolving epidemiology. These findings underscore the need for improved recognition and resource planning for these treatable neurologic disorders.