Diagnosis of paraproteinemic neuropathy: Room for improvement.

Objective: To report our institutional experience with paraproteinemic neuropathy.

Methods: We reviewed the charts of patients evaluated at our tertiary, academic neuromuscular clinic for neuropathy between 2017 and 2019 and selected those with a serum monoclonal protein. We collected patients' characteristics and reviewed their initial diagnoses and eventual outcomes.

Results: Fifty-four of 410 patients with neuropathy (13%) had a monoclonal protein. Of these patients, 25% had not had SPEP or IFE checked prior to referral. FLC was not checked in any of the patients prior to referral. The neuropathy was felt to be related to the monoclonal protein in 24 patients (44%). Ten patients (19%), had been misdiagnosed either because they were not screened for monoclonal protein or the monoclonal protein was considered a MGUS. AL amyloid and POEMS syndrome were the most frequently missed diagnoses.

Conclusion: The diagnosis of paraproteinemic neuropathy was missed in nearly one in five patients in our cohort. Failure to accurately characterize a paraproteinemic neuropathy can have devastating effect on patients as some have underlying malignancies. We propose that testing serum free light chains in patients with peripheral neuropathy of unknow etiology, when SPEP/IFE are normal, may reduce the rate of misdiagnosis. Furthermore, patients with refractory CIDP should be carefully screened for POEMS syndrome.