Prevalence and Spectrum of Neuropathies in a Cohort of 585 Patients With Immunoglobulin A Monoclonal Gammopathy

Abstract

Background

Neuropathies associated with IgA monoclonal gammopathy are poorly understood, and the interpretation of the presence of such gammopathy in a patient with neuropathy may be challenging.

Methods

The neurological and hematological features of all patients newly diagnosed with IgA gammopathy by immunofixation in our center from January 2016 to December 2020 were retrospectively analyzed. Patients with neuropathy were identified through the medical records. The etiology was reviewed by two neurologists and classified into three groups: (i) IgA-related neuropathies, (ii) IgA-unrelated neuropathies with an identified alternative etiology, and (iii) neuropathies of uncertain relationship with IgA (NURIA) based on a negative extensive work-up.

Results

Among 585 patients with IgA gammopathy, 79 had neuropathy (14%). Neuropathy was IgA-related in 10 patients (13%): eight AL amyloidosis and two POEMS. In this group, the core features were neuropathic pain, autonomic dysfunction, fatigue or weight loss, and a lambda light chain. IgA-unrelated neuropathies were more frequent (N = 64, 81%), encompassing mainly chemotherapy-induced (N = 34) and diabetic (N = 15) neuropathies. Five patients (6%) were classified as NURIA: four had mild sensory-predominant length-dependent axonal neuropathy, and one had severe, progressive, motor-predominant axonal neuropathy.

Conclusions

In patients with IgA gammopathy, neuropathies have a low prevalence and a wide etiological spectrum. AL amyloidosis and POEMS syndrome are rare but crucial to identify, as disease-modifying treatments are available. Future studies should help better characterize the rare cases of neuropathy with an uncertain relationship to IgA gammopathy.