To the editor: A 56-year old woman on daratumumab, denosumab, lenalidomide, and dexamethasone for relapsed multiple myeloma (MM) presented to the emergency department with generalized weakness and watery diarrhea for 3-4 days. She denied preceding symptoms, unusual exposures, or sick contacts, and had no smoking, alcohol, drug use, recent travel, or notable family history. She was initially tachycardic, tachypneic, and febrile without rigors. She developed bilateral facial and upper extremity twitching with occasional full-body rhythmic jerking.