Chronic inflammatory demyelinating polyradiculoneuropathy secondary to immune checkpoint inhibitors in melanoma patients.

IMPORTANCE: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an autoimmune neurological disorder that is characterized by symmetrical progressive worsening or relapsing weakness and numbness of the limbs. There are no reliable diagnostic tests or definitive diagnostic criteria, and the diagnosis remains one of excluding other cases of polyneuropathy. Typical treatment for CIDP includes corticosteroids, intravenous immunoglobulin (IVIG), and plasma exchange. Little is known about CIDP as a treatment complication of immune checkpoint inhibitors (ipilimumab and nivolumab). This report will be helpful in increasing awareness and knowledge about this unique entity. OBSERVATIONS: We describe two cases of CIDP secondary to treatment with combined ipilimumab and nivolumab in patients with metastatic melanoma that were successfully treated with prednisone and IVIG. Conclusion and Relevance: This report illustrates that treatment with immune checkpoint inhibitors can lead to CIDP that can be successfully treated with complete resolution of symptoms. CIDP secondary to checkpoint inhibitors may have unique features such as low-grade lymphocytic pleocytosis on CSF evaluation as well as severe neuropathic pain as an early presenting symptom. Additionally, it is interesting to note that both patients presented in this report remained melanoma-free on follow-up more than 16 months later.