Clinical reasoning: a 40-year-old man with CIDP-like illness resistant to treatment

CIDP mimics: a case series

Background

To report our experience with a group of patients referred for refractory CIDP who fulfilled “definite” electrodiagnostic EFNS criteria for CIDP but were found to have an alternate diagnosis.

Methods

Patients who were seen between 2017 and 2019 for refractory CIDP that fulfilled “definite” electrodiagnostic ENFS criteria for CIDP, but had an alternate diagnosis, were included. Patients who correctly had CIDP, anti MAG neuropathy, or MMN with conduction block, were excluded from the study. Demographics, clinical and electrophysiological characteristics, pertinent workup, final alternate diagnoses, and outcomes were collected.

Results

Seven patients were included: POEMS (n = 5), CANOMAD (n = 1), and neurolymphomatosis (n = 1). Most patients reported neuropathic pain and leg swelling (n = 6) or significant weight loss (n = 4). All patients had a monoclonal protein, and most patients who were tested had an elevated VEGF and CSF cyto-albuminologic dissociation. Electrophysiology showed pronounced intermediate more than distal demyelination, and axonal loss in the lower extremities. Response to steroids or IVIG varied, but some patients did respond to these treatments, especially early in the disease.

Conclusion

Pain, systemic symptoms, suggestive electrophysiological findings, and/or a serum monoclonal protein should raise suspicion for CIDP mimics. Initial response to steroids or IVIG, over reliance on CSF, and electrophysiology findings can all be misleading.

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.