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Case Report of Delayed Encephalopathy From Pembrolizumab
Christopher Kotsis1, Brandon H Hidaka2
1Mayo Clinic Health System, Eau Claire, Eau Claire, Wisconsin, Kotsis.Christopher@mayo.edu.
Introduction:
Pembrolizumab is an immune checkpoint inhibitor (ICI) used to treat many types of advanced cancer. ICIs can cause encephalopathy, a severe immune-related adverse event, which is a diagnosis of exclusion. Pembrolizumab immune-related adverse events typically develop early (within a few months) in treatment; presentation after a year is extremely rare.
Case Presentation:
A 70-year-old White female with metastatic endometrial cancer treated with pembrolizumab for 19 months presented with generalized weakness that rapidly progressed to confusion, delusions, and hallucinations.
Discussion:
After ruling out other causes of encephalopathy via broad-based testing of blood and cerebrospinal fluid and imaging, her neurologic status improved after treatment with high-dose glucocorticoids and intravenous immunoglobulin.
Conclusions:
Pembrolizumab is an ICI that can cause encephalopathy, which is challenging to diagnose. While immune-related adverse events typically emerge soon after starting treatment, pembrolizumab-induced encephalopathy can be delayed significantly.
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