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Abstract: SA-PO490

Cadmium Toxicity From Cigarettes Causing Proximal Renal Tubular Acidosis and Severe Symptomatic Hypokalemia

Session Information

Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders

  • 1002 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Clinical

Author

  • Baker, Lyle Wesley, Mayo Clinic, Jacksonville, Florida, United States
Introduction

Heavy metal toxicity is an underrecognized cause of proximal renal tubular acidosis (RTA). Acquired proximal RTA is commonly caused by paraprotein disease, autoimmune disease, & medications. Heavy metals like cadmium can cause proximal RTA. This author presents two cases of cadmium toxicity from cigarette smoking causing proximal RTA and severe hypokalemia presenting as muscle weakness.

Case Description

Case 1: 57-year-old female with COPD and >40 pack-year smoking history, admitted for general weakness. She actively smoked 2 packs per day (PPD).

Case 2: 66-year-old female with COPD and >50 pack-year smoking history, admitted for lower extremity weakness. She actively smoked 1 PPD.

Both patients denied diarrhea, vomiting, and use of laxatives or diuretics. Both patients had unremarkable vitals & exam was significant for 4/5 muscle strength of extremities. Admission labs (Table 1) revealed severe hypokalemia, hypophosphatemia, & non-anion gap metabolic acidosis. Urine studies (Table 1) including urine potassium-to-creatinine ratio, β2-microglobulin, & retinol-binding protein-to-creatinine ratio were suggestive of renal potassium wasting, proximal tubulopathy, & RTA. Testing for paraprotein & autoimmune disease was unremarkable. Review of medications did not identify an offending agent. Heavy metals screen in both patients revealed elevated urinary cadmium confirming cadmium toxicity.

Discussion

The kidneys are a primary target organ for chronic cadmium toxicity. Inhalation of tobacco smoke is the main source of cadmium exposure in smokers; inhalation from smoking 1 PPD is between 1-3 μg. The critical urinary cadmium-creatinine ratio associated with renal tubular injury is 2-10 μg/g. These two cases highlight the importance of recognizing chronic cadmium toxicity from cigarette smoking as a rare cause of proximal RTA.

Table 1: Labs
 Case #1Case #2Reference
Potassium (mmol/L), serum<1.51.63.6-5.2
Phosphorus (mg/dL), serum1.00.92.5-4.5
Bicarbonate (mmol/L), serum201722-29
Serum Anion Gap1197-15
Urine Anion Gap9.122 
24 Hour Urine Potassium (mEq)108->30 suggestive of renal potassium wasting in setting of hypokalemia
Urine Potassium-to-Creatinine Ratio (mEq/g)15355.9>13 suggestive of renal potassium wasting in setting of hypokalemia
β2-Microglobulin (μg/L), urine>20,000>20,000<300
Retinol-Binding Protein-to-Creatinine Ratio (μg/g), urine173,200178,800<190
Cadmium-to-Creatinine Ratio (μg/g), urine6.29.0<0.6