Clinical Reasoning: A 59-year-old woman with multiple myeloma and lower extremity weakness and numbness

Abstract

A 59-year-old woman with a history of stage 3 immunoglobulin G (IgG) lambda multiple myeloma (MM) on treatment with bortezomib and dexamethasone, chronic lower back pain, and chronic but improving bilateral lower extremity weakness and numbness presented with 2 to 3 weeks of worsening lower extremity weakness and numbness. Prior to presentation, the patient had been hospitalized for sepsis and cardiac arrest. Weakness affected the left lower extremity before progressing to the right lower extremity, whereas numbness was present in both feet. There was no bowel or bladder incontinence, saddle anesthesia, preceding trauma, or history of radiation therapy. The bilateral lower extremity weakness and numbness resulted in gait impairment and falls, which prompted admission for further investigation. Notably, bortezomib had been started 4 months prior to presentation. Initial examination revealed cachexia, bilateral thigh atrophy, and bilateral lower extremity flaccid weakness, along with areflexia. The weakness was symmetric proximally (Medical Research Council 1/5 in bilateral hip flexion and knee flexion and extension) but asymmetric distally (0/5 in right dorsiflexion; 2/5 in right plantarflexion, left dorsiflexion, and plantarflexion). In addition to the weakness, the patient exhibited symmetric sensory loss in the distal lower extremities. There was no sensory level. Examination of the upper extremities was normal, including motor, sensory, and reflexes.