A case report of nephronophthisis type 1 (NPHP1) complicated with tethered cord in a pediatric patient: clinical phenotype and rapid progression to end stage renal disease

Abstract

Nephronophthisis (NPHP) is an autosomal recessive cystic kidney disease and a leading cause of pediatric end stage renal disease (ESRD). Tethered cord is one of the important causes of neurogenic bladder in children, and the latter is a risk factor for secondary chronic kidney disease (CKD). The co-occurrence of nephronophthisis type 1 (NPHP1) and tethered cord has never been reported previously. Here, we present a rare case of a 7-year-old girl diagnosed with NPHP1 complicated with tethered cord. The patient was admitted for incidentally identified renal dysfunction (serum creatinine 101.7 µmol/L, estimated glomerular filtration rate [eGFR] 45.2 mL/min/1.73 m²) after an abdominal pain visit. She had a long history of enuresis and daytime urinary incontinence. Magnetic resonance imaging showed separation of the cauda equina from the filum terminale, and abdominal computed tomography revealed mild bladder wall thickening with a measured thickness of 4 mm under adequate bladder distension. Nevertheless, no vesicoureteral reflux or structural abnormalities were detected by voiding cystourethrogram. The typical clinical manifestations of NPHP1, such as polydipsia and polyuria, were absent. The only urinary abnormality was a relatively low urine specific gravity. Genetic testing confirmed a homozygous pathogenic deletion of exons 1–20 in the NPHP1 gene. The patient underwent neurosurgical intervention for tethered cord, but her renal function progressed rapidly from CKD stage 3 to pre-ESRD within 5 months. To the best of our knowledge, this is the first case report of genetically confirmed NPHP1 complicated with tethered cord in a pediatric patient. This case highlights that genetic testing should be performed promptly in children with unexplained CKD, even when secondary renal injury factors are identified.