To describe a case of CIDP with an evolving electrodiagnostic profile and a relapsing course that was manifested after 1.5 years of Nivolumab therapy.

Immune checkpoint inhibitors (ICIs) like Nivolumab are a cornerstone in treating relapsed/refractory Hodgkin's Lymphoma. However, they can trigger severe immune-related adverse events (irAEs). Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is a rare but serious neurological irAE.

A 33-year-old female with a history of Hodgkin's Lymphoma since 2015, refractory to initial therapies and treated with an autologous stem cell transplant in 2020, was started on Nivolumab. After 09 months of therapy, with her lymphoma in remission, she developed progressive sensorimotor symptoms starting in August 2023, including widespread paresthesia and significant proximal weakness, leading to the cessation of Nivolumab in September 2023.

Initial investigations in October 2023 included a normal electroneuromyography (ENMG) and unremarkable spine MRI, but cerebrospinal fluid (CSF) analysis revealed albuminocytologic dissociation. She was treated with high-dose intravenous methylprednisolone followed by an oral prednisone taper, with partial improvement. After tapering off prednisone, she experienced a severe relapse in February 2024, requiring hospitalization. During her admission, a repeat ENMG revealed a subacute, axonal, sensory-motor polyradiculopathy. The patient was treated with a 5-day course of Intravenous Immunoglobulin (IVIG) followed by another course of high-dose methylprednisolone, leading to substantial clinical improvement.

Outpatient management was defined through a multidisciplinary discussion with the hematology department, with a confirmed diagnosis of Nivolumab-induced CIDP. The therapeutic plan included scheduling the initiation of Azathioprine as a steroid-sparing agent.

This case underscores several critical points in the management of neurological irAEs. First, severe neuropathies like CIDP can develop late in the course of immunotherapy and even worsen after its discontinuation. Second, initial neurophysiological studies (ENMG) may be normal. This highlights the need for vigilant long-term monitoring and a multidisciplinary approach for patients treated with ICIs.