Ultra-rare severe kidney dysplasia mimicking salt-wasting tubulopathy associated with TFCP2L1 gene variants.

Rare monogenic diseases are increasingly identified in children with chronic kidney disease. We describe a consanguineous preterm male infant with a clinical picture of advanced kidney dysfunction and severe renal salt-wasting, highly suggestive of prenatal onset Bartter syndrome. Patient's follow-up was characterized by severe polyuria; episodes of hyponatremia, hypokalemia, and hypochloremia; and metabolic alkalosis and hyperuricemia. We found a homozygous pathogenic variant in the TFCP2L1 gene, a transcription factor required for normal kidney development, that regulates acid-base and salt-water homeostasis. To our knowledge, there is only one published case of a child with TFCP2L1 gene pathogenic variants with a similar phenotype. This report adds evidence to TFCP2L1 as a cause of monogenic kidney disorders. Rare kidney dysplasias may manifest as phenocopies of primary tubulopathies. Genetic diagnosis plays a major role and should be carefully considered in patients with refractory course to standard treatment to facilitate management and family counselling.