Title : A rare case of the medullary cystic kidney disease, nephronophthisis (NPHP)

Background: NPHP is a rare, autosomal recessive genetic disorder characterized by tubulointerstitial injury and cystic changes in the kidneys, leading to end-stage renal disease in children and adolescents. Pathogenic variants in the NPHP3 gene manifest with hepatobiliary and neurological abnormalities in addition to renal disease.

Case report: A four-month-old male infant had experienced persistent jaundice since birth; genetic testing revealed a pathogenic variant in the NPHP3 gene, and both parents were identified as carriers of this gene. As the disease progressed, renal function deteriorated, and persistent hyperkalemia, hypoproteinemia, hypoalbuminemia, severe normocytic anemia, proteinuria, albuminuria, and microhematuria, as well as hepatobiliary abnormalities, were observed. Despite treatment, the blood potassium level failed to normalize and hyperkalemia worsened, reaching 9.94 mmol/L; ventricular tachycardia developed, and defibrillation was performed. Abdominal ultrasound revealed markedly increased parenchymal echogenicity in both kidneys, loss of corticomedullary differentiation, multiple cystic changes, and cystic-like dilation of the intrahepatic bile ducts.

Conclusion: This case demonstrates that renal medullary cysts can manifest in the neonatal period as severe renal dysfunction and extrarenal abnormalities, particularly involving the hepatobiliary system. For children presenting with combined renal and hepatic abnormalities, early suspicion of hereditary ciliopathy and the use of genetic testing are crucial for confirming the diagnosis.

Keywords: NPHP3, ciliopathy, hyperkalemia, renal dysfunction, infant.

My name is Purevjargal and I am the daughter of Munkhpurev. I was born on October 12, 1989, in Ulaanbaatar, Mongolia, into a working-class family. I completed my primary and secondary education during the period of 2008–2014. Driven by a strong passion for healthcare, I pursued my higher education at the Mongolian National University of Medical Sciences (MNUMS) from 2016 to 2018, successfully graduating with a degree in Pediatric Nursing.

Committing myself to continuous professional development and specialized clinical practice, I have successfully attained the following post-graduate qualifications:

• Pediatric Cardiology: Specialized qualification acquired in 2019.
• Pediatric Intensive Care: Specialized training completed in 2020.
• Pediatric Neurology: Advanced clinical specialization completed in 2026.

With a solid foundational background in pediatric healthcare and a proven track record of continuous professional specialization, I am highly motivated to further advance my knowledge, skills, and clinical competencies through this training program.