(Kiosk 3) Progressive Lower Extremity Weakness in Patient Initiated on Checkpoint Inhibitor Immunotherapy: A Case Report

Case Diagnosis: 82-year-old male with past medical history significant for mixed small and non-small cell lung cancer with metastasis to the brain started on an immune checkpoint inhibitor approximately two weeks prior to developing new progressive bilateral lower extremity weakness with imaging significant for T10-L1 nonspecific myelitis.

Case Description or Program Description: Patient presented to the emergency department for progressive lower extremity weakness which initially started 2 weeks following initiation of immunotherapy regimen of carboplatin, etoposide, and acetozilumab. He had completed 8 visits of outpatient physical therapy with noticeable progressive lower extremity weakness and fatigue. Loss of bowel and bladder function with decreased sensation prompted the patient to seek further care.

Setting: Tertiary care hospital

Assessment/Results: Physical examination revealing symmetric bilateral lower extremity weakness. MRI of thoracic and lumbar spine initially showing abnormal central cord signal from T10 through L1 concerning nonspecific myelitis. Lumbar puncture with mildly elevated protein, but otherwise unremarkable. Autoimmune laboratory work up did not reveal an obvious source. Symptoms were refractory to stress dose steroids, which prompted five cycles of plasmapheresis exchange providing minimal improvements. Repeat MRI of thoracic spine 2 weeks after previous showing progressed hyperintense changes up to T5.

Discussion (relevance): The progressive lower extremity weakness with bowel and bladder incontinence with hyperintense changes seen on spinal imaging provides diagnosis of thoracolumbar myelitis. Given the timeframe of symptoms two weeks following treatment with an immune checkpoint inhibitor, the diagnosis of autoimmune myelitis is considered. Although rare, there have been several cases documented of autoimmune myelitis caused by this class of immunotherapies.

Conclusions: This case brings awareness to adverse effects that may manifest following treatment with immunotherapy and specifically toward immune checkpoint inhibitors. As these therapies become more widespread as mainstay treatments of malignancies, it is important for physiatrists to be mindful of lesser known side effects and to remove offending agents early in course.