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Chronic Inflammatory Demyelinating Polyradiculoneuropathy-Like Neuropathy in Heterozygous C9orf72 Mutation: A Case
Valentin Loser1, Vadim Afanasiev2, Alex Vicino1
1Nerve Muscle Unit, Neurology Service, Department of Clinical Neurosciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
Introduction:
C9orf72 repeat expansion is usually associated with amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and ALS/FTD overlap. We report an atypical neuromuscular presentation of C9orf72 repeat expansion.
Case Presentation:
A 68-year-old patient developed a sensorimotor polyneuropathy with slow continuous worsening over 3 years. Symptoms started in the left foot and slowly extended to all four limbs. Nerve conduction studies were consistent with a non-length-dependent predominantly axonal sensorimotor polyneuropathy, with some additional demyelinating features (proximal temporal dispersion and F-wave latency prolongation). Electro-clinical presentation fulfilled EAN/PNS 2021 criteria for CIDP, but the patient was not responsive to IVIg. RT-PCR revealed a heterozygous pathogenic expansion of the C9orf72 gene. The patient's father and brother died from ALS. At onset, his brother also had sensorimotor involvement and was misdiagnosed with CIDP.
Conclusion:
This case may expand the phenotypic spectrum associated with C9orf72 repeat expansion. The initial phenotype could be a non-length-dependent sensorimotor polyneuropathy with demyelinating features that potentially mimics CIDP.

