Pure motor-variant CIDP associated with immune checkpoint inhibitor therapy

Introduction: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an autoimmune disease with many possible etiologies. There are only a few reports of CIDP secondary to the use of immune checkpoint inhibitor therapy. The aim is to describe a case of CIDP secondary to the treatment of metastatic melanoma with immune checkpoint inhibitors (ipilimumab and nivolumab). Case report: A 52-year-old male patient, with arterial hypertension and hypothyroidism, presented with paresthesia and pain in the hands and forearms in November/22, that progressively spread and affected the feet in a one-month period. He then presented proximal and distal tetraparesis in January/23, leading him to depend on a wheelchair. At the time, he was being treated with immunotherapy for metastases in the pectoral muscles due to a melanoma. Symptoms’ onset and progression coincided with the therapy infusions. On examination, there were a grade 4 strength in flexion, extension, abduction and adduction of the thighs and grade 5 in other movements, with global areflexia and tactile hypoesthesia in the feet. Cerebrospinal fluid examination (CSF) showed 11 cells, predominantly with lymphocytes, and 283 mg/dL of proteins. Electromyographic studies revealed focal demyelinating neuropathy of the medians at the wrist level, with moderate to severe intensity on the right and moderate on the left, suggestive of pure motor-variant CIDP. Methylprednisolone 1g/day was given for five days with significant improvement of the condition. Results: The 2021 EFNS/PSN criteria provide diagnostic guidelines for CIDP based on clinical, electromyographic and CSF studies. Conclusion: CIDP secondary to the use of immune checkpoint inhibitors has distinct characteristics such as lymphocytic pleocytosis with slightly increased CSF cellularity and severe neuropathic pain as an initial symptom.