Genetic background of neonatal hypokalemia

Neonatal hypokalemia (defined as a serum potassium level <3.5 mEq/L) is the most common electrolyte disorder encountered in clinical practice. In addition to common secondary causes, primary genetic etiologies are also closely associated with hypokalemia. Currently, a systematic characterization of these genetic disorders is lacking, making early recognition challenging and clinical management uncertain. This review will aid clinicians by summarizing the genetic background of neonatal hypokalemia from two aspects: (1) increased excretion of K+, whereby genetic factors primarily lead to increased renal Na+ influx, decreased H+ efflux, or reduced Cl- influx, ultimately resulting in increased K+ efflux; and (2) decreased extracellular distribution of K+, whereby genetic factors result in abnormalities in transmembrane ion channels, reducing outward potassium currents or generating inward cation leak currents. We describe over ten genetic diseases associated with neonatal hypokalemia, which involve pathogenic variants in dozens of genes and affect multiple target organs, including the kidneys, intestines, and skeletal muscle. For example, in the renal tubules, pathogenic variants in the SLC12A1 gene encoding the Na+-K+-2Cl(-) cotransporter lead to renal K+ loss, causing Bartter syndrome type I; in intestinal epithelial cells, pathogenic variants in the SLC26A3 gene result in a defective Cl--HCO3- exchanger, causing congenital chloride diarrhea; and in skeletal muscle, pathogenic variants in the CACNA1S gene impact membrane calcium ion channels resulting in hypokalemic periodic paralysis. Given the wide variety of organs and genetic alterations that can contribute to neonatal hypokalemia, we believe this review will provide valuable insights for clinical diagnosis and treatment.