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Nephronophthisis: Juvenile and Infantile Form

Definition of Nephronophthisis

Nephronophthisis is an autosomal recessive group of diseases that lead to tubulointerstitial nephritis and the formation of multiple renal cysts. Depending on the genetic defect, currently, nine different forms are known. Nephronophthisis leads to end-stage renal disease at different ages (Solomon et al., 2009).

Epidemiology:

• 10% of children with end-stage renal disease are suffering from nephronophthisis
• Nephronophthisis is the most common form of inherited renal failure before the age of 30 years.

Causes, Pathology, and Sign and Symptoms of Nephronophthisis

Known Gen Mutations

Known genetic defects of nephronophthisis cause a deficiency of the primary cilium, which leads to disturbed cell polarity, tubular atrophy, disruption of the basement membrane and interstitial fibrosis. The mutated gene NPHP1, which encodes a defective form of nephrocystin-1, causes juvenile nephronophthisis. Mutations of the gene NPHP2 cause the infantile form. Seven other gene defects with partially different onsets of the disease have been discovered (NPHP3–9).

Juvenile Nephronophthisis

Children with juvenile nephronophthisis have normal-sized kidneys at birth; symptoms start at 6–20 years with polydipsia and polyuria. Interstitial nephritis with tubular dilatation and atrophy develops. In end-stage disease, small-sized kidneys have multiple cysts of 1–10 mm in size. The electrolyte loss prevents hypertension. End-stage renal disease occurs 5–10 years after the onset of symptoms.

Infantile nephronophthisis

Infantile nephronophthisis leads to end-stage renal disease before the age of 5 years.

Associated Diseases:

• Retinitis pigmentosa (Senior-Løken syndrome)
• Laurence-Moon-Bardet-Biedl syndrome (obesity, debility, polydactyly, retinitis pigmentosa and hypogenitalism)
• Orthopedic diseases
• Liver fibrosis

Diagnosis Workup of Nephronophthisis

Ultrasound of the kidneys:

Small-sized kidneys with hyperechogenic parenchyma. Cysts are often seen only in the later disease stages.

Genetic diagnosis:

Mutations in the NPHP gene family.

Renal biopsy:

in unclear cases.

Treatment of juvenile Nephronophthisis

In the early stages of the disease, treat hypovolemia, electrolyte disorders, anemia, and hypertension. Later in the course of the disease, dialysis and renal transplantation are necessary.

References

  Deutsche Version: Nephronophthise