Persistent renal dysfunction post-chemotherapy: a diagnostic conundrum in pediatric cancer survivorship - a case report.

Background: Late-onset type II Bartter syndrome is an exceedingly rare condition, with only six documented cases presenting symptoms and signs beyond infancy. We report a unique case of late-onset type II Bartter syndrome with an atypical presentation and clinical course following chemotherapy treatment during childhood.

Case Presentation: A 10-year-old boy, diagnosed with hepatoblastoma at age 2 and treated with cisplatin and epirubicin, presented with polyuria, polydipsia, failure to thrive, and electrolyte imbalances. He exhibited hypokalemia, metabolic alkalosis, and elevated urinary excretion of sodium, chloride, calcium, and magnesium. Whole exome sequencing and Sanger sequencing identified compound heterozygous variants in the KCNJ1 gene, confirming the diagnosis of type II Bartter syndrome. The patient's clinical presentation was distinct from previously reported cases, with an absence of nephrocalcinosis, unusually small and hyperechoic kidneys, and a substantial decline in kidney function. Treatment included oral potassium supplementation, spironolactone, and angiotensin-converting enzyme inhibitors.

Conclusions: This case highlights the importance of considering late-onset Bartter syndrome in patients with a history of chemotherapy presenting with persistent electrolyte imbalances and ongoing renal dysfunction. The atypical features and rapid progression of chronic kidney disease in this patient may be attributed to the deleterious nature of the identified variants and the potential impact of previous chemotherapy on kidney susceptibility to damage. Careful monitoring and management of electrolyte imbalances and renal function are crucial in such cases.