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Abstract: PO1929

Idiopathic Hypokalemia in Lupus Nephritis: A Previously Unrecognized Entity

Session Information

Category: Glomerular Diseases

  • 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Adomako, Emmanuel A., University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States
  • Bilal, Saira, George Washington University Medical Faculty Associates, Washington, District of Columbia, United States
  • Liu, Yu-Lun, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States
  • Malik, Ayesha M., Aga Khan University, Karachi, Pakistan
  • Sambandam, Kamalanathan K., University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States
Background

The lupus nephritis (LN) population at Parkland Hospital is among the largest in the country. During the course of usual care in this population, we encountered a phenomenon of unexplained hypokalemia that has never been previously described. Here we begin to phenotype this cohort by comparing it to a group of LN controls as well as LN with distal renal tubular acidosis (RTA).

Methods

From our population of 403 LN patients followed in the Parkland Health and Hospital System, we identified a cohort of 20 patients with idiopathic hypokalemia (HK). This cohort is compared to 90 LN controls (control) and 10 LN patients with distal RTA (RTA). In contrasting the three groups, the Chi-squared test or Fisher’s exact test were used for categorical data and the one-way ANOVA or Kruskal-Wallis test was used for continuous measures. For paired comparisons of continuous variables between the groups, the student’s t-test was employed

Results


The HK cases had lower mean serum potassium compared to control and RTA (3.24 vs 4.06 vs 3.75 mmol/L, respectively; P< 0.001). The mean serum bicarbonate was normal in HK and control but lower in RTA (25.83 vs 25.20 vs 19.28 mmol/L, respectively; P< 0.001). The urine pH was abnormally high only in the RTA group (6.13 vs 6.22 vs 6.68; P= 0.012). The mean serum magnesium was modestly lower in HK compared to control-nml and control-RTA (1.75 vs 1.97 vs 1.97 mg/dL; P= 0.002)
There were differences in serologic markers of autoimmunity. Compared with control, both HK and RTA were more likely to be seropositive for anti-SSA (P= 0.002 and 0.015, respectively). In contrast, compared to controls, only HK expressed a higher rate of anti-RNP seropositivity (P= 0.002) and only control-RTA had a higher rate of anti-SSB positivity (P= 0.044).

Conclusion


A syndrome of idiopathic hypokalemia was revealed in 20/403 (5%) of patients within our lupus nephritis population and is distinct from the RTA that is known to rarely occur in lupus. This phenomenon has not been previously described. We speculate that idiopathic hypokalemia is the result of a novel target of autoimmunity in lupus affecting renal tubular potassium transport.

Funding

  • Other NIH Support