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Kidney Week

Abstract: FR-PO572

Hypokalemia as the Smoking Gun of Paraneoplastic Syndrome

Session Information

  • Trainee Case Reports - III
    October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Trainee Case Reports

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Scovner, Katherine Mikovna, BWH/MGH, Boston, Massachusetts, United States
  • Li, Li, Brigham and Women's Hospital, Brookline, Massachusetts, United States
  • Bonventre, Joseph V., Brigham and Women's Hospital, Brookline, Massachusetts, United States
Introduction

Ectopic secretion of ACTH (EAS) is commonly associated with small cell lung cancer but rare with other lung cancers. The present case is that of an individual with EAS leading to hypokalemia in the setting of lung adenocarcinoma.

Case Description

A 66-year-old woman presents with metastatic lung adenocarcinoma (poorly differentiated) diagnosed 2 years prior to admission. She had been treated with carboplatin and taxol. She presents with hypokalemia (K 2.6mmol/L despite K supplementation of 80meq per day). Hypokalemia was noted at the time of carboplatin therapy but resolved following its discontinuation. Hypokalemia was noted again at the time of the diagnosis of brain metastasis. Other labs were notable for Mg 1.8mg/dL, bicarbonate 33mmol/L, pH 7.51, and WBC 34.4K/uL with neutrophil predominance. Urine K was 92mmol/L and transtubular K gradient ((urine K/plasma K)/(urine osm/plasma osm)) was 26.2. Plasma cortisol was 46.5ug/dL at 7pm when ACTH was 67pg/mL. Morning cortisol after 1mg and 8mg dexamethasone were 38.1ug/dL and 32.9ug/dL respectively. Urine free cortisol was 650mcg/24 hours. Renin and aldosterone levels were both below lower limits of assay detection. Brain MRI showed no pituitary pathology to suggest Cushing disease. She was thus diagnosed with EAS. The patient underwent bilateral laparoscopic adrenalectomy, and potassium normalized. She then pursued hospice care as there were no more chemotherapeutic options.

Discussion

Although rare among non-small cell lung cancer patients, 13 cases of EAS with non-small cell lung cancer had been reported as of 2012.
Hypokalemia due to platinum-based chemotherapy tends to coexist with hypomagnesemia (platinum decreases Mg, which inhibits the Na+K+ATPase and K is lost in urine through potassium channels in the thick ascending limb).
The patient had hypokalemia as well as leukocytosis at the time of diagnosis of brain metastasis. Trends in K and WBC over time may help predict progression of malignancy in the setting of EAS.
Bilateral adrenalectomy represents an option for control of EAS, but expected survival post-operatively should be considered before proceeding.