Presentations

Abstract

Introduction:

Rituximab (RTX) is a chimeric monoclonal antibody used for the treatment of malignancies and autoimmune diseases. Severe hypokalemia, a rare adverse effect of RTX treatment, has previously been reported only three times in the literature. We describe a patient who developed severe proximal muscle weakness hours after completing his second RTX infusion for acute relapse of membranous nephropathy (MN) and was found to have critically low potassium levels requiring ICU admission.

Case Information:

A 50-year-old male with a past medical history of bilateral renal vein thrombosis and MN presented with proximal muscle weakness shortly after completing his second RTX infusion for acute MN relapse. Originally diagnosed with MN 15 years ago, the patient maintained stable renal function (Cr 1.5-1.8 mg/dL, proteinuria 1.5-2.0 g/day) for the last 5 years without MN relapse. He was started on RTX infusion after developing an AKI on CKD stage 3 (Cr 3.3 mg/dL) with severe proteinuria >8 g/day, hypoalbuminemia 2.9 g/dL, in the setting of worsening MN on kidney biopsy 2 months prior. The patient tolerated his first infusion well without significant reactions but developed severe weakness in his arms and legs beginning 5 hours after his second infusion. Common adverse effects of RTX, such as infusion-related reactions, lymphopenia, neutropenia, or signs of infection were not experienced by our patient. He was found to have severe hypokalemia (2.1 mg/dL) with mild hypomagnesemia (1.4 mg/dL). He was later transferred to the intensive care unit due to refractory hypokalemia. During his ICU course, his serum potassium was aggressively repleted orally and through central line placement, and closely monitored with serial BMP. The patient's potassium and magnesium returned to within normal ranges after 24 hours, and he demonstrated significant improvement in his symptoms. He was transferred out of the ICU and discharged a couple of days later with scheduled oral potassium repletion.

Discussion/Clinical Findings:

This Case Report highlights a rare association of life-threatening hypokalemia after RTX infusion. Our patient did not receive potassium supplementation until 30 hours after symptom onset, ultimately requiring emergent attention and an ICU admission. Given the rapid onset and severity of this reaction, which can unexpectedly occur despite tolerating RTX previously, a low threshold for ICU admission should be adopted to avoid life-threatening complications. Close monitoring of symptoms after RTX infusions is essential to prevent this rare but serious complication, and further studies are needed to elucidate RTX's complete effect on renal tubules.

Conclusion:

Hypokalemia induced by RTX may be rapid and severe, even if the medication has previously been tolerated well. Any clinical or laboratory evidence of down-trending potassium in a patient receiving RTX warrants a high index of suspicion for a rapid decrease in serum potassium and a low threshold for ICU admission.