Abstract: SA-PO490
Cadmium Toxicity From Cigarettes Causing Proximal Renal Tubular Acidosis and Severe Symptomatic Hypokalemia
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports
November 05, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
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 #1 | Case #2 | Reference | |
| Potassium (mmol/L), serum | <1.5 | 1.6 | 3.6-5.2 |
| Phosphorus (mg/dL), serum | 1.0 | 0.9 | 2.5-4.5 |
| Bicarbonate (mmol/L), serum | 20 | 17 | 22-29 |
| Serum Anion Gap | 11 | 9 | 7-15 |
| Urine Anion Gap | 9.1 | 22 | |
| 24 Hour Urine Potassium (mEq) | 108 | - | >30 suggestive of renal potassium wasting in setting of hypokalemia |
| Urine Potassium-to-Creatinine Ratio (mEq/g) | 153 | 55.9 | >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), urine | 173,200 | 178,800 | <190 |
| Cadmium-to-Creatinine Ratio (μg/g), urine | 6.2 | 9.0 | <0.6 |