Science News: Insights Into Refractory Chronic Inflammatory Demyelinating Polyneuropathy: A Comprehensive Real-World Study

Summary: In this study, the authors sought to delineate the clinical characteristics, disease progression patterns, and potential risk factors associated with refractory chronic inflammatory demyelinating polyneuropathy (CIDP), as well as the electrophysiological features of this condition.

The authors applied the 2021 European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) clinical criteria for CIDP to a cohort of neuropathy patients sourced from a national rare disease center database.

Treatment response was defined as an improvement confirmed objectively by either: (1) A minimum increase of 4 points on the Medical Research Council sum score, (2) A reduction of at least 1 point on the Inflammatory Neuropathy Cause and Treatment (INCAT) disability score, or (3) A decrease of at least 1 point on the modified Rankin Scale.

Refractory CIDP was characterized by: (1) Lack of response to at least two out of three initial treatment options (corticosteroids, intravenous immunoglobulin (IVIG), or therapeutic plasma exchange (TPE)) or relapse during tapering of medication; or (2) Dependence on at least two out of three initial treatment options simultaneously for maintaining treatment efficacy; or (3) No response to at least one out of three initial treatment options combined with the addition of an immunosuppressive drug (such as rituximab, azathioprine, mycophenolate mofetil, methotrexate, fingolimod, or cyclophosphamide).

Additionally, within the refractory CIDP subgroup, four distinct disease progression patterns were identified: relapsing–remitting, stable, secondary progressive, and primary progressive forms.

Among the 58 CIDP patients included, 33 were classified as having non-refractory CIDP while 25 were categorized as having refractory CIDP. Within the refractory CIDP group, 42.86% exhibited a relapsing–remitting pattern, 23.81% displayed a secondary progressive pattern, 23.81% maintained a stable course, and 14.29% presented with a primary progressive pattern.

According to the 2021 EAN/PNS guideline, among the refractory CIDP patients, 14 (56.0%) were diagnosed with typical CIDP, while 11 patients presented with CIDP variants (including 7 with distal CIDP, 1 with multifocal CIDP, 1 with focal CIDP, 1 with motor CIDP, and 1 with sensory CIDP).

In comparison to non-refractory CIDP patients, those with refractory CIDP exhibited longer disease duration (48.96 ± 33.72 vs. 28.33 ± 13.72 months) and more severe functional impairment as evidenced by both Medical Research Council sum score and INCAT disability score. Electrophysiological studies also indicated greater axonal impairment and more severe demyelination in refractory CIDP cases compared to non-refractory ones.

Motor nerve conduction studies revealed significantly lower ulnar compound muscle action potential, prolonged ulnar and median distal latency, reduced median conduction velocity, and prolonged F-wave latency in the refractory CIDP group compared to the non-refractory group. Additionally, sensory nerve conduction studies indicated a more pronounced reduction in conduction velocity on the ulnar nerve in refractory CIDP patients compared to their non-refractory counterparts. Disease duration emerged as an independent risk factor for refractory CIDP.

Comments: This study provided a comprehensive description of refractory CIDP, addressing its clinical features, classification of clinical course, electrophysiological characteristics, and prognostic factors.

The findings indicated that refractory CIDP patients exhibited a longer disease duration, more pronounced functional impairment, significant axonal damage, and more severe demyelination based on electrodiagnostic assessments.

A primary limitation of the study lies in its retrospective nature, small sample size, and reliance on data from a single center located in a region with restricted availability and accessibility issues regarding IVIG treatment. Refractory CIDP is a challenging subset of CIDP. It does not respond well to immune therapy and causes substantial disability. This study contributes to a better understanding of this challenging subset of CIDP and might be informative for management and treatment strategies.

Article of similar interest: Godil J, Barrett MJ, Ensrud E, Chahin N, Karam C. Refractory CIDP: clinical characteristics, antibodies and response to alternative treatment. J Neurol Sci. (2020) 418:117098. doi: 10.1016/j.jns.2020.117098.